Chemical substance In organic chemistry, there can be more than one chemical compound with the same composition and molecular weight. Generally, these are called isomers. Isomers usually have substantially different chemical properties, and often may be isolated without spontaneously interconverting. A common example is glucose vs. fructose. The former is an aldehyde, the latter is a ketone. Their interconversion requires either enzymatic or acid-base catalysis. However, tautomers are an exception: the isomerization occurs spontaneously in ordinary conditions, such that a pure substance cannot be isolated into its tautomers, even if these can be identified spectroscopically or even isolated in special conditions. A
Prefixes in Hebrew Hebrew serve multiple purposes. A prefix can serve as a conjunction, preposition, definite article, or interrogative. Prefixes are also used when conjugating verbs in the future tense and for various other purposes. These prefixes (Hebrew: תְּחִלִּית "t'chilit") often come from loanwords from English (Latin, Greek, etc...) which are especially prevalent with technical and academic terms. Other prefixes are native to Hebrew (ex. rav). When the Hebrew prefix does not line up in similarity to the English, Greek, or Latin one that is because it is of Hebrew origin. Prefixes in Hebrew There are several prefixes in the Hebrew language which