—v.i. 1. to interchange repeatedly and regularly with one another in time or place; rotate (usually fol. by with): Day alternates with night. 2. to change back and forth between conditions, states, actions, etc.: He alternates between hope and despair. 3. to take turns: My sister and I alternated in doing the dishes. 4. Elect.to reverse direction or sign periodically.
5. Ling.to occur as a variant in alternation with another form.
—v.t. 1. to perform or do in succession or one after another: to alternate comedy acts; to alternate jogging and walking. 2. to interchange successively or regularly: to alternate hot and cold compresses.
—adj. 1. being in a constant state of succession or rotation; interchanged repeatedly one for another: Winter and summer are alternate seasons. 2. reciprocal; mutual: alternate acts of kindness. 3. every second one of a series: Read only the alternate lines. 4. constituting an alternative: The alternate route is more scenic. 5. alternative (defs. 4, 6).
6. Bot. a. placed singly at different heights on the axis, on each side in succession, or at definite angular distances from one another, as leaves.
b. opposite to the intervals between other organs: petals alternate with sepals.
—n. 1. a person authorized to fill the position, exercise the duties, etc., of another who is temporarily absent; substitute.
2. Theat. a. either of two actors who take turns playing the same role.
b. an understudy.