The words alternate and alternative are closely related, but they can’t be used interchangeably in all cases.
As a verb, alternate (the last syllable rhymes with late) means to happen by turns, to take turns, or to exchange places.
As a noun, alternate (the last syllable rhymes with net) refers to a substitute–someone who is prepared to take the place of someone else.
As an adjective, alternate (again, the last syllable rhymes with net) means occurring by turns or being one of two or more choices.
As a noun, alternative refers to one of two or more possibilities or something that remains to be chosen.
As an adjective, alternative means offering a choice (between or among two or more possibilities) or something different from the usual or conventional.
See the usage notes below.
Each year, the names of hurricanes alternate between male and female.
Each year since 1989, a turkey–and its alternate–have been pardoned by the president. An alternate is chosen just in case the first bird can’t perform its duties.
“I remember when you used to keep the car on the street and switch it from one side of the street to the other every night, because of the alternate-side parking rules.”
(Calvin Trillin, Tepper Isn’t Going Out. Random House, 2001)
A nurse and a physical therapist visit my grandmother on alternate days.
The alternative was to attempt to land the plane on a highway.
My brother attends an alternative school for bright and independent students.