What is contrast in identical environments?

Definition
	Contrast in identical environments is the difference between two phonetically similar segments that occur in two separate words and have identical adjacent sounds.
	If neither segment has been modified or affected by its environment, the segments are separate phonemes.

Examples (English)
	The segments [l] and [r] contrast in identical environments in the following minimal pair.
	[lip] [rip]
	The implication is that /l/ and /r/ are separate phonemes.

Examples (Cashinahua, Peru/Brazil)
	The segments [s ] and [S] contrast in identical environments in the following minimal pair:
	[m&u0268;su] 'swollen hand' [m&u0268;Su] 'black, dark'
	The implication is that /s/ and /S/ are separate phonemes.