alternate Definition

alternate
adj

1. Said of two feelings, states, conditions, etc: arranged or coming one after the other in turn.

Example: alternate layers of pasta and sauce
2. Every other; one out of two.

Thesaurus: rotating, every other, every second, alternating, different.
3. bot.
Said of leaves, petals, etc: appearing singly and regularly at either side of a stem.

verb, tr & intr alternated, alternating

1. Said of two things: to succeed or make them succeed each other by turns.

Example: Helen and Mike alternate their days off
Thesaurus: fluctuate, oscillate, take turns, vary, rotate, interchange, substitute, transpose.
2. Said of an electric current, etc: to reverse direction in a regular pattern. See alternating current.

noun

1. A substitute, especially a person who covers in someone's absence.

Thesaurus: replacement, substitute, equivalent, double.

Derivative: alternately
adverb

Etymology: 16c: from Latin alternare, alternatum to do one thing after another.

Phrasal Verb: alternate between something and something else

To change from one thing to another by turns.
Example: He alternates between fits of depression and periods of euphoria

Phrasal Verb: alternate from something to something else

To change from it to another.
Example: Her mood swings alternate from one extreme to the other

Phrasal Verb: alternate or alternate something with someone or something

To swap or substitute with them or it, especially regularly or continually.

Info:

These words are often confused with each other.