IDIOMS

An idiom is an expression, word, or phrase that has a figurative meaning that is comprehended in regard to a common use of that expression that is separate from the literal meaning or definition of the words of which it is made. There are estimated to be at least 25,000 idiomatic expressions in American English.
In linguistics, idioms are usually presumed to be figures of speech contradicting the principle of compositionality; yet the matter remains debated. John Saeed defines an “idiom” as words collocated that became affixed to each other until metamorphosing into a fossilised term. This collocation — words commonly used in a group — redefines each component word in the word-group and becomes an idiomatic expression. The words develop a specialized meaning as an entity, as an idiom. Moreover, an idiom is an expression, word, or phrase whose sense means something different from what the words literally imply. When a speaker uses an idiom, the listener might mistake its actual meaning, if he or she has not heard this figure of speech before. Idioms usually do not translate well; in some cases, when an idiom is translated into another language, either its meaning is changed or it is meaningless.

For Example:
"Pick Someone's brain" (When someone isnt being smart)
"Run with the hare and hunt with the hounds" (do what you need to do with the correct people)