Definition of "Formation" :

noun: the act of forming or establishing something

noun: the act of fabricating something in a particular shape

noun: creation by mental activity

"The formation of sentences."

noun: a particular spatial arrangement

noun: an arrangement of people or things acting as a unit

"A defensive formation."

noun: (geology) the geological features of the earth

noun: natural process that causes something to form

"The formation of gas in the intestine."