# Property
A property is any of several on-or-off traits of the hero or a monster. Properties include the resistances, the effects of rings, the temporary effects of certain potions, negative effects (as confusion, stoning), and others. A property may be intrinsic or extrinsic.
Intrinsic and extrinsic properties are binary; you either have it or you don't. Thus numerical traits (as alignment record, dexterity, luck, prayer timeout, etc.) are not properties in this sense. Enlightenment will reveal many properties of the hero, along with some other traits.

Contents

1 Intrinsic versus extrinsic
2 List of properties

2.1 Intrinsic properties
2.2 Extrinsic properties
2.3 Intrinsics that always time out
2.4 Intrinsics that cause harm on time out

3 Commentary
4 Source code

4.1 References

Intrinsic versus extrinsic
In NetHack, an intrinsic is any property that your character has internally, while an extrinsic is any property that your character derives from using, carrying or wearing an item.
You gain an extrinsic when you wield, wear or put on an item that provides it. The item is typically a ring, amulet, armor or artifact. For example, the amulet of ESP or the helm of telepathy can grant extrinsic telepathy; the extrinsic goes away when you take off the item. Some nice quest artifacts provide an extrinsic when carried; in that case, the extrinsic goes away when you drop or lose the artifact, or place it in a container.
There are more ways to gain an intrinsic.

You might gain it as an innate property of your role or race. For some innate properties, you need to first reach a certain experience level. For example, a Barbarian starts with poison resistance and gains intrinsic speed at level 7.
You might gain it "from outside". The principal ways to do this are crowning, eating certain corpses, eating jewelry or sitting on thrones.
The gremlin has an attack that may steal one of eleven intrinsics. Also, you can lose an innate property if something drains you below the required level. Eating a disenchanter corpse may also remove one of the same intrinsics that gremlin attacks affect.

List of properties
The following tables provide a brief description of each property that the hero might have, and some notable sources of that property. (The property may have other sources.) The individual articles for each property might provide more details.
The left column also gives the associated constant from prop.h, if any. The right column may refer to a monster flag (like M1_FLY); then you may search monst.c to find a monster with that flag for polymorph.

Intrinsic properties
It is possible to receive any of these properties as intrinsics that never time out. Some are also available as extrinsics, or as temporary intrinsics. This list includes each property that may be intrinsic, even if the only way is to eat the correct ring. (Eating a ring has a chance of failing to convey the property!)

Common nameof property

DescriptionNotable sources

fire resistanceFIRE_RES

Prevents fire damage, but does not fireproof your inventory.
Be a Monk at level 11, or a Priest at level 20
Eat a corpse (see fire resistance page)
Put on or eat a ring of fire resistance
Polymorph into a resistant monster (MR_FIRE)

cold resistanceCOLD_RES

Prevents cold damage, but does not protect your potions.
Be a Valkyrie
Be a Monk at level 13
Eat a corpse (see cold resistance page)
Put on or eat a ring of cold resistance
Polymorph into a resistant monster (MR_COLD)

sleep resistanceSLEEP_RES

Prevents sleep. Alternatively, free action works for potions only.
Be an elf at level 4
Eat a corpse (see sleep resistance page)
Eat a ring of free action (wearing it would provide free action)
Polymorph into a resistant monster (MR_SLEEP)

disintegration resistanceDISINT_RES

Prevents instadeath from black dragon breath (or use reflection to block the breath); also the only way to prevent instadeath from wide-angle disintegration beams.
Eat a black dragon corpse
Polymorph into a resistant monster (MR_DISINT)

shock resistanceSHOCK_RES

Prevents damage from electric attacks, but does not defend rings or wands.
Be a Monk at level 15
Eat a corpse (see shock resistance page)
Put on or eat a ring of shock resistance
Polymorph into a resistant monster (MR_ELEC)

poison resistancePOISON_RES

Prevents poisoning, also prevents the instadeath from poison.
Be an orc, Barbarian, or Healer
Be a monk at level 3 or a Tourist at level 20
Eat a corpse (see poison resistance page)
Wear an amulet versus poison or ring of poison resistance
Polymorph into a resistant monster (MR_POISON)

regenerationREGENERATION

Increases the rate of recovery of your hit points, so that they sooner return to maximum.
Put on or eat a ring of regeneration
Wield the Staff of Aesculapius
Polymorph into a monster with M1_REGEN; examples include trolls, vampires and werecreatures

searchingSEARCHING

Automatically search squares around you, increasing the chance that you notice hidden doors or traps.
Be a Ranger
Be a Monk at level 9, or an Archaeologist, Rogue, or Tourist at level 10
Put on or eat a ring of searching
Wield Excalibur

see invisibleSEE_INVIS

Allows you to see invisible monsters (and in SLASH'EM, invisible objects).
Be a Ranger at level 15
Quaff potion of see invisible (only permanent if blessed)
Put on or eat a ring of see invisible
Eat a stalker corpse while invisible
Polymorph into a monster with M1_SEE_INVIS
Drink from a fountain.

invisibleINVIS

Makes you invisible. Monsters may struggle to find you and miss with their attacks.
Quaff a potion of invisibility (only permanent if blessed)
Zap oneself with a wand of make invisible
Wear a cloak or ring of invisibility.
Eat a stalker corpse while temporarily invisible
Polymorph into a stalker (causes stunning) or a black light
Invoke the Orb of Detection

teleportation/teleportitisTELEPORT

Every few turns, randomly teleports you around the dungeon level.
(Sometimes) eat a leprechaun, nymph, tengu, or the Wizard of Yendor
Put on or eat a ring of teleportation
Polymorph into a monster with M1_TPORT

teleport controlTELEPORT_CONTROL

When you teleport, allows you to choose your destination tile.
Be a Monk or Wizard at level 17
(Sometimes) eat a tengu or the Wizard of Yendor
Put on or eat a ring of teleport control
Carry the Master Key of Thievery
Polymorph into a tengu (M1_TPORT_CNTRL)

polymorph/polymorphitisPOLYMORPH

Every few turns, randomly polymorphs you into another monster type.
Put on or eat a ring of polymorph

polymorph controlPOLYMORPH_CONTROL

When you polymorph, allows you to choose the type of monster to become.
Put on or eat a ring of polymorph control
(In SLASH'EM) be a Doppelganger at level 9

levitationLEVITATION

You float in the air, and cannot reach the floor! However, you can pass over moats, trap doors and pits (except the pits in Sokoban, due to air currents).
Quaff a potion of levitation (temporary)
Cast the spell from a spellbook of levitation (temporary)
Wear a ring of levitation or boots of levitation
Eat a ring of levitation (temporary)
Invoke the Heart of Ahriman

stealthSTEALTH

Allows you to move around quietly, so that your steps do not wake sleeping monsters.
Some roles have innate stealth (see stealth page)
Wear elven boots, elven cloak, or ring of stealth
Receive a favor from your god when praying

aggravate monsterAGGRAVATE_MONSTER

Increases probability that nearby sleeping monsters notice you and wake.
(For all heroes but cavemen and orcs) eating cat or dog meat, or eating your own race
Sacrificing a dead pet at an altar
Wear or eat a ring of aggravate monster

conflictCONFLICT

Monsters will attack other nearby monsters (including you), disregarding their tame/peaceful/hostile status.
Put on or eat a ring of conflict
Invoke the Sceptre of Might

protectionPROTECTION

Indicates that you either have intrinsic divine protection, or wear an item of protection, for the purpose of the enlightenment message.
Buy divine protection by donating to priests
Wear a cloak of protection or ring of protection
Receive a favor from your god when praying

protection from shape changersPROT_FROM_SHAPE_CHANGERS

Forces shapeshifters and chameleons to stay in normal form.
Put on or eat a ring of protection from shape changers

warningWARNING

Labels unseen, undetected nearby monsters with a danger indicator from 1 to 5.
Be a Monk at level 7, some roles at level 15
Put on or eat a ring of warning
Carry the Master Key of Thievery or the Orb of Fate

hungerHUNGER

Increases the rate that you lose nutrition. This is bad, unless you are trying to make room for your next meal.
Put on or eat a ring of hunger

telepathyTELEPAT

Intrinsic telepathy allows you to sense most monsters (except mindless monsters), but only when you are blind.
Eat a floating eye (100% chance) or (master) mind flayer corpse (50% chance, 100% if at maximum intelligence)
Receive a favor from your god when praying
Extrinsic telepathy also functions in a limited radius when you are not blind.

Wear an amulet of ESP or helm of telepathy
Carry the Longbow of Diana, the Orb of Detection, the Magic Mirror of Merlin, or the Platinum Yendorian Express Card

speedFAST

Intrinsic speed makes you fast, allowing four moves for every three turns.
Zap yourself with a wand of speed monster
Eat a quantum mechanic corpse to toggle the intrinsic
Receive a favor from your god when praying
Extrinsic speed, and temporary intrinsic speed, make you very fast, allowing five moves every three turns.

Quaff a potion of speed
Wear speed boots

food appraisal

Before eating something, warns you of any bad effects that might result, and allows you to abort. Lost after activating once.
Read a blessed scroll of food detection
Cast detect food at skilled or expert

unbreathingMAGICAL_BREATHING

Allows you to survive without breathing. You can go underwater. You will not choke on your food.
Put on or eat an amulet of magical breathing
Polymorph into a breathless monster (M1_BREATHLESS)

amphibiousness

Allows you to breathe both in the air and underwater. You can go underwater.
Polymorph into an amphibious monster, such as any ; (M1_AMPHIBIOUS)
Be breathless

jumpingJUMPING

Allows you to land on another tile in one move.
Be a Knight
Wear jumping boots
Read spellbook of jumping (provides a spell instead of the property)

infravisionINFRAVISION

Your eyes sense the heat from warm monsters, making them visible to you, even in unlit places.
Play as a dwarf, elf, gnome or orc (these have M3_INFRAVISION)
Polymorph into a monster with M3_INFRAVISION

Extrinsic properties
There are no sources that provide any of these properties as an intrinsic (without polymorphing), but they have extrinsic sources:

Common nameof property

DescriptionNotable sources

acid resistanceACID_RES

Prevents acid damage (from yellow dragon breath, or from eating acidic corpses), but does not rustproof your armor.
Wear an alchemy smock or yellow dragon scale mail
Polymorph into a resistant monster (MR_ACID)

stoning resistanceSTONE_RES

Prevents the stoning process. This is one way to fight cockatrices and chickatrices.
Polymorph into a resistant monster (MR_STONE), such as a cockatrice, elemental, gargoyle or black naga
(In SLASH'EM) wear an amulet versus stone

sliming resistance

Provides immunity to the sliming process; this protects against the slime attack of the green slime.[1]
Polymorph into a green slime, fire vortex, flaming sphere, fire elemental or salamander
Be unchanging

drain resistanceDRAIN_RES

Protects against loss of experience levels, for example from the drain life attack of monsters. Prevents instadeath from drain below level 1.
Wield Stormbringer or Excalibur or the Staff of Aesculapius
Polymorph into any undead monster, demon or werecreature[2]

adornmentADORNED

Indicates that you wear a ring of adornment (of any enchantment). This intrinsic allows an enlightenment message to be displayed.
Wear a ring of adornment (note: charisma is modified by the ring's enchantment)

reflectionREFLECTING

Bounces gaze and ray attacks away from you, so that they do not affect you.
Wear silver dragon scale mail
Wear a shield of reflection or amulet of reflection
Wield the Longbow of Diana
Polymorph into a silver dragon (not the baby form)

life savingLIFESAVED

When you die, the worn amulet of life saving will resurrect you.
Wear an amulet of life saving (do not eat this amulet!)

magic resistanceANTIMAGIC

Prevents damage from certain traps, from magic missile and certain other magic attacks, and rays/fingers of death, among other useful benefits.
Wear a cloak of magic resistance or gray dragon scale mail
Wield Magicbane
Carry certain quest artifacts

phasingPASSES_WALLS

You can walk through walls. This is useful for taking shortcuts without digging them, and fleeing from certain places. However, this property has no effect in Sokoban.
Polymorph into a xorn or earth elemental
(In SLASH'EM) cast the spell passwall.

hallucination resistanceHALLUC_RES

Prevents the effects of hallucination.
Wield Grayswandir

fumblingFUMBLING

Causes you to sometimes trip while walking, accidentally drop items, fall down stairs, and have other such problems.

Wear gauntlets of fumbling or fumble boots

water walkingWWALKING

You can cross water by walking on its surface (as an alternative to using levitation, magical breathing or swimming). If the boots are fireproof, they may also be used to cross lava.
Wear water walking boots

displacementDISPLACED

Produces a displaced image of you on a nearby square, such that monsters sometimes attack the image and miss you.

Wear a cloak of displacement
(In SLASH'EM) wear shimmering dragon scale mail

clairvoyanceCLAIRVOYANT

Every few turns, the map of the area around you appears in your mind. This helps explore new areas and discover hidden paths.

Buy temporary clairvoyance by donating to priests
Be a Wizard and wear a cornuthaum
Carry the Amulet of Yendor

energy regenerationENERGY_REGENERATION

Your power increases toward maximum at a much faster rate, allowing you to frequently cast spells (if you have enough nutrition).
Carry the Eye of the Aethiopica

half spell damageHALF_SPDAM

Carry the Orb of Detection, the Platinum Yendorian Express Card, the Orb of Fate or the Eye of the Aethiopica

half physical damageHALF_PHDAM

Carry the Master Key of Thievery or the Orb of Fate

sickness resistanceSICK_RES

Provides complete immunity to sickness--both illness and food poisoning.
Polymorph into a ghoul or any fungus

free actionFREE_ACTION

Prevents paralysis in most cases. Makes the potion of sleeping harmless, but does not prevent other forms of sleep. Reduces stunning from monster spells to one turn.
Wear a ring of free action (eating it would grant sleep resistance)

swimmingSWIMMING

Enables you to swim across water. This differs from levitation (to float across water) and breathless (to go underwater).
Polymorph into a swimming monster (M1_SWIM)
Ride a swimming steed
(In SLASH'EM) wear gauntlets of swimming

sustain abilityFIXED_ABIL

Prevents changes to your six attributes. Prevents the effects of exercise and abuse.
Put on a ring of sustain ability (eating never works)

flyingFLYING

Enables you to fly above the ground. Flight is better than levitation, because you may reach the ground and fly down stairs.
Polymorph into a flying monster, such as a dragon (M1_FLY)
Ride a flying steed
(In SLASH'EM) wear an amulet of flying

unchangingUNCHANGING

Holds you to your current form. Use this to prevent unwanted polymorph, or to remain forever in your polymorphed form.
Wear an amulet of unchanging

slow digestionSLOW_DIGESTION

Decreases the rate that you lose nutrition, allowing you to survive longer before starvation. Also prevents purple worms from digesting you.
Put on a ring of slow digestion (ring is inedible)

warned of monster typeWARN_OF_MON, WARN_UNDEAD

Detects all monsters on the dungeon level that match certain monster types.

To be warned of orcs, wield Sting
(In SLASH'EM) To be warned of undead, be an Undead Slayer at level 1, or Necromancer at level 3

Intrinsics that always time out
You may receive any of these properties in this table as a temporary intrinsic, but not as a permanent intrinsic. After a specific number of turns, you lose the temporary intrinsic. That may be well, because most of these properties have bad effects; you would want them to wear off over time.

Common nameof property

DescriptionNotable sources

stunSTUNNED

Movement commands may cause you to step in a random direction, and you may hit pets by mistake. Direction of Zapping, spellcasting and firing also has a high chance of being randomized. Prevents teleport control.
Attempt to cast a forgotten spell (sometimes).
Eat a bat, giant bat or stalker corpse.
Get hit by the Stun monster spell, or the stunning gaze attack of Baalzebub and Archons.
Polymorphing into a bat, giant bat, vampire bat, raven or stalker.

confusionCONFUSION

Among other effects, you will mispronounce any scroll that you read (causing the scroll to have an alternate effect), and you will have trouble with spells and spellbooks.
Attempt to cast a forgotten spell (sometimes).
Get hit by the confusing gaze attack of an umber hulk

blindnessBLINDED

Disables your eyes, blocking your sight (unless you wear the Eyes of the Overworld). Intrinsic blindness will heal eventually, or you may use a cure such as a carrot.
Attack of a raven, explosion of a yellow light.
The only cure for extrinsic blindness is to remove whatever is blocking your eyes. Cream pie will eventually fall off and can also by removed by the #wipe command.

Wear a blindfold or a towel.
Polymorph into a monster without eyes (M1_NOEYES).

restful sleepSLEEPING

You keep falling asleep.
Wear an amulet of restful sleep.

paralysis

You become immobile and miss a number of turns.
Quaff a potion of paralysis, or let a monster throw it at you.

wounded legsWOUNDED_LEGS

Among other effects, you can carry less weight, and you cannot jump or kick.

Jump out of a bear trap.
Kick wall, object, or nothing (sometimes).
Get hit by a xan's attack.
Step on a land mine.

hallucinationHALLUC

Gives a random appearance to any monster or object on the map, so that you do not know who or what you see. In SLASH'EM, hallucination also distorts the view of objects on the same square as you, including your inventory.
Eat a yellow mold or violet fungus.
Explosion of a black light.

slippery fingersGLIB

Causes wielded objects to drop from your grasp.
Eat greasy food from a tin.
Applying a cursed can of grease or choosing "-" as a target for a non-cursed one.

invulnerabilityINVULNERABLE

Blocks all damage and prevents most causes of death.
(In vanilla) only available as the "shimmering light" during prayer.
(In SLASH'EM) a weaker form of invulnerability can be obtained by quaffing a potion of invulnerability.

monster detectionDETECT_MONSTERS

Detect all monsters on the dungeon level. This property is only available as a temporary intrinsic.
Quaff a potion of monster detection.
Read a spellbook of detect monsters and cast the spell.

Intrinsics that cause harm on time out
These temporary intrinsics do not only time out and go away, they also cause do something (typically to cause instadeath) when they time out. When you have one of these properties, you only have some number of turns to remove the property and avoid its time-out effect.

Common nameof property

DescriptionNotable sources

sicknessSICK

A fatal illness; you must cure this or it becomes an instadeath.
Receive food poisoning by eating a very old corpse
Receive illness from the attack of Demogorgon, Juiblex, Scorpius or Pestilence

stoningSTONED

Gradual stiffening will turn you into a statue (causing instadeath).
Attack from a monster wielding a cockatrice corpse

nausea/vomitingVOMITING

Can cause stun and confusion; when nausea times out, you spew part of your food and lose some nutrition.[3]
Eat a tripe ration or a rotten egg

strangulationSTRANGLED

Your amulet will strangle you to instadeath in five turns, unless you can somehow remove it before then.

Wear an amulet of strangulation

slimeSLIMED

Green slime will overtake your body and kill you, unless you can somehow remove the slime or gain sliming resistance before that happens.
Attack from a green slime
Eat a green slime corpse

Commentary
The adjective intrinsic refers to something that is internal, inherit, within the body. We also use the term as a noun. The antonym of intrinsic is extrinsic.
Oddly, sometimes we also use the term "intrinsic" to refer to any property, whether that property is intrinsic or extrinsic. For example, we might refer to an "intrinsic" from a ring, though the ring is external to the character. This leads to oxymoronic phrases such as "extrinsic intrinsic".
The usage of "intrinsic" to mean "extrinsic" occurs in other pages on this wiki, and even within the source code of NetHack. For example, the comment at the top of wield.c refers to wielded weapons conveying intrinsics, though they would actually convey extrinsics. The set_artifact_intrinsic function in artifact.c is another example of this usage. The mintrinsics field of struct monst stores information about both intrinsic and extrinsic resistances of the monsters.[4]
The struct prop that tracks properties has only separated "intrinsic" and "extrinsic" since NetHack 3.3.0.[5]
One can justify the use of "intrinsic" to mean "extrinsic". For example, an amulet versus poison may be extrinsic to your body, but when you wear it, the effect spreads inside your body and becomes intrinsic. When you eat that kobold shaman corpse, or land on poison in a spiked pit, then the poison enters your body but has no effect. There must be some intrinsic defense in your body that stops the poison, though the ring remains outside on your finger. This explanation would not work so well for an amulet of reflection.
If you quaff a potion that provides a property, it is an intrinsic or extrinsic property? One argument states that the contents of the potion enters your body, so the property must be intrinsic. (A look at struct prop supports that argument.) The other argument states any property from an item, including a potion, is an extrinsic. The potion of blindness seems to grant intrinsic blindness (not extrinsic blindness, which you could #wipe away), but the potion of speed seems to grant extrinsic speed, equivalent with speed boots.
If you acquire a property through polymorph, it is an intrinsic or extrinsic property? One argument notes that the property is intrinsic to your current form; the other argument provides that your current form is extrinsic to your true form.

Source code
For details, see prop.h
The source code defines most of the properties at prop.h, line 8. Each property has a representative integer constant. Particularly in objects.c and artilist.h, the integer constants assign the properties granted by using certain items. The integer constants also serve as array indexes into the u.uprops, an array of struct prop that records the source of each of the hero's intrinsics and extrinsics.
While food appraisal and paralysis do not have constants in prop.h, they behave like other intrinsics, thus their inclusion in the lists on this page.

References

↑ mhitu.c, line 1524, mondata.h, line 51

↑ mondata.c in NetHack 3.4.3, line 73

↑ timeout.c in NetHack 3.4.3, line 51

↑ monst.h, line 63, mondata.h, line 14, mondata.c, line 23, worn.c, line 260

↑ NetHack 3.2.0/you.h, line 108, NetHack 3.3.0/prop.h, line 78