Definition from Wiktionary, the free dictionary
alternant (not comparable)
- Alternating from one row of a matrix to another.
- (geology) Composed of alternate layers, like certain rocks.
alternant (plural alternants)
- (linguistics) An alternate form or allomorph.
- (mathematics) A determinant which is an alternating function.
Derived terms 
- Present participle of alternar.
- Present participle of alterner.
- third-person plural present active indicative of alternō