Real Dictionary

formation
A rock or cloud formation is rock or cloud of a particular shape or structure.
If people or things are in formation, they are arranged in a particular pattern as they move.
the act of giving or taking form, shape, or existence [...]
uncountable noun: The formation of an idea, habit, relationship, or character is the process of developing and establishing it.
uncountable noun: The formation of something is the starting or creation of it.

formation in American English
a forming or being formed
noun: the act or process of forming or the state of being formed

formation in British English
noun: the act of giving or taking form, shape, or existence

formation in the Oil and Gas Industry
noun: A formation is an area of rock that is of one type and is distinctive and continuous enough to be mapped.