A metrical foot consisting of an unaccented syllable followed by an accented syllable. The words “unite” and “provide” are both iambic. It is the most common meter of poetry in English (including all the plays and poems of William Shakespeare), as it is closest to the rhythms of English speech. In Robert Frost’s “After Apple Picking” the iamb is the vehicle for the “natural,” colloquial speech pattern:

       My long two-pointed ladder’s sticking through a tree
       Toward heaven still,
       And there’s a barrel that I didn’t fill
       Beside it, and there may be two or three
       Apples I didn’t pick upon some bough.
       But I am done with apple-picking now.
       Essence of winter sleep is on the night,
       The scent of apples: I am drowsing off.