Metrical units are the building blocks of poetry and other forms of literature. Iambs, FEET, iambi, and moras are all metrical units used to measure the rhythm of a poem or other written work. An iamb is a two-syllable unit consisting of an unstressed syllable followed by a stressed syllable. A foot is a two-syllable unit consisting of a stressed syllable followed by an unstressed syllable. An iambi is a three-syllable unit consisting of two unstressed syllables followed by a stressed syllable. Finally, a mora is a single syllable unit that can be either stressed or unstressed.