"My Last Duchess" is written in rhymed iambic pentameter, which maintains an even beat throughout the poem.

Iambic pentameter has been said to be the most natural cadence of the English language. It consists of an iamb, which is two syllables: an unstressed followed by a stressed. An example of an iamb might be the words "a heart," drawn from the lines: "A heart-how shall I say? too soon made glad." The rhythm of the first two words can be scanned with emphasis indicating a stressed syllable, and an unstressed syllable:

a heart.

Pentameter means that there are five groups of iambs in a line of poetry; each group is called a foot.

"My Last Duchess" also uses rhymed couplets, meaning that every two lines end with a rhyme. For example, the first two lines of the poem end with the words "wall" and "call." The poetic device...