What is a preposition?

According to the Merriam-Webster Learners Dictionary, a preposition is: “a word or group of words that is used with a noun, pronoun, or noun phrase to show direction, location, or time, or to introduce an object”.

Prepositions express relationships such as space (place, position, direction), time, or figurative location. A preposition always has an object (usually a noun or pronoun). The preposition and its object (and any modifiers) are together called a prepositional phrase.

For example:

  • The preposition “on” in “The flask is on the lab bench” shows location.
  • The preposition “in” in “The centrifuge will finish in 3 hours” shows time.


Why are prepositions important?

Prepositions are often called the biggest small words in English because although they are generally short words, they are very important to the meaning of the sentence. A misused preposition can make a big difference between a clearly stated sentence and a confusing jumble of words. When used properly, however, prepositions provide the glue between parts of a sentence that allows you to share your scientific research more precisely and professionally.

Prepositions are used to connect nouns, pronouns, or phrases (called the object of the preposition) to other words within a sentence. They reveal the temporal, spatial, or logical relationship of their object to another word or part of the sentence. For example:

  • The flask is on the lab bench. (space)
  • The waste basket is below the lab bench. (space)
  • The centrifuge is beside the lab bench. (space)
  • The fume hood is across from the lab bench. (space)
  • He broke the flask during the experiment. (time)

In each of these examples, the preposition (bold) is used to show the relationship in space or time of one noun (red) to another noun (blue). The second noun (blue) is called the object of the preposition. Note that a preposition can comprise multiple words (e.g., across from).


How do I use prepositions?

Prepositions are usually short words, and are normally placed directly in front of nouns, noun phrases, or pronouns. Because they are somewhat vague, learning about prepositions and using them correctly in English sentences takes practice. Here are some rules for using prepositions:

  • Prepositions are followed by a noun, and never by a verb.
  • A prepositional phrase begins with a preposition and ends with the preposition’s object (either a noun or pronoun).
  • The subject of the sentence cannot be part of a prepositional phrase.
  • Verbs cannot be part of a prepositional phrase.

There are hundreds of prepositions in the English language. Understanding how to use each one may seem a bit daunting. Most of these prepositions fall into one of three categories: those denoting space (place, position, or direction), time, or other relationships. Some prepositions are formed using two or three words – like “across from” or “in front of.”


Common English Prepositions


Space Time Other
Place Position Direction






away from











in front of









out (of)



























The following three tables provide examples of the use of many commonly used prepositions (source:


Prepositions – Space (Place, Position, and Direction)  
English Usage Example  
in room, building, street, town, country in the kitchen, in London  
book, paper, etc. in the book  
car, taxi in the car, in a taxi  
picture, world in the picture, in the world  
at meaning next to, by an object at the door, at the station  
for table at the table  
for events at a concert, at the party  
place where you are to do something typical (watch a film, study, work) at the cinema, at school, at work  
on attached the picture on the wall  
for a place with a river London lies on the Thames.  
being on a surface on the table  
for a certain side (left, right) on the left  
for a floor in a house on the first floor  
for public transport on the bus, on a plane  
for television, radio on TV, on the radio  
by, next to, beside left or right of somebody or something Jane is standing by / next to / beside the car.  
under on the ground, lower than (or covered by) something else the bag is under the table  
below lower than something else but above ground the fish are below the surface  
over covered by something else put a jacket over your shirt  
meaning more than over 16 years of age  
getting to the other side (also across) walk over the bridge  
overcoming an obstacle climb over the wall  
above higher than something else, but not directly over it a path above the lake  
across getting to the other side (also over) walk across the bridge  
getting to the other side swim across the lake  
through something with limits on top, bottom and the sides drive through the tunnel  
to movement to person or building go to the cinema  
movement to a place or country go to London / Ireland  
for bed go to bed  
into enter a room / a building go into the kitchen / the house  
towards movement in the direction of something (but not directly to it) go 5 steps towards the house  
onto movement to the top of something jump onto the table  
from in the sense of where from a flower from the garden  


Prepositions – Time

English Usage Example  
on days of the week on Monday  
in months / seasons in August / in winter  
time of day in the morning  
year in 2006  
after a certain period of time (when?) in an hour  
at for night at night  
a certain point of time (when?) at half past nine  
since from a certain point of time (past till now) since 1980  
for over a certain period of time (past till now) for 2 years  
ago a certain time in the past 2 years ago  
before earlier than a certain point of time before 2004  
to telling the time ten to six (5:50)  
past telling the time ten past six (6:10)  
to/till/until marking the beginning and end of a period of time from Monday to/till Friday  
till/until in the sense of how long something is going to last He is on holiday until Friday.  
by in the sense of at the latest I will be back by 6 o’clock.  
up to a certain time By 11 o'clock, I had read five pages.  


Other important prepositions

English Usage Example  
from who gave it a present from Jane  
of who/what does it belong to a page of the book  
what does it show the picture of a palace  
by who made it a book by Mark Twain  
on walking or riding on horseback on foot, on horseback  
entering a public transport vehicle get on the bus  
in entering a car  / Taxi get in the car  
off leaving a public transport vehicle get off the train  
out of leaving a car  / Taxi get out of the taxi  
by rise or fall of something prices have risen by 10 percent  
traveling (other than walking or horseback riding) by car, by bus  
at for age she learned Russian at 45  
about for topics, meaning what about we were talking about you  


One important guideline for using prepositions is that they are usually followed by nouns (any form of noun, including noun phrases and pronouns). Examples of forms of nouns acceptable for this purpose are:
  • Noun
scientist, article, hypothesis
  • Proper Noun (name)
Einstein, Albert
  • Pronoun
you, him, us
  • Noun group
our current research
  • Gerund
Many prepositions are also used idiomatically, meaning that there is no specific rule to guide you but that some expressions must be memorized, such that certain verbs and adjectives are followed by specific prepositions. Here are some examples:
  • applied to
  • depend on
  • identical to
  • opposed to
  • preoccupied with
  • prohibited from
  • recover from
Avoid using unnecessary prepositions. If the meaning of the sentence is not changed by omitting the preposition, then the preposition is not necessary.
  Incorrect: We discussed about the experiment.
  Correct: We discussed the experiment.
  Incorrect: She entered into the room.
  Correct: She entered the room.

Prepositions serve as a bridge, connecting thoughts and phrases so your reader can follow your writing more easily. When used correctly, they will enhance your scientific articles, linking details that explain and amplify your written content.