The poem consists of three stanzas of four lines each. Technically, these stanzas are quatrains, because they consist of four lines. Similar in structure and meter to a sonnet, a traditional love poem, Yeats uses iambic pentameter in “When You Are Old,” but does not finish the poem with a couplet that would put the poem at fourteen lines. Iambic pentameter is a line that has 10 syllables in it, with 5 metric “feet,” or small groups of syllables paired together. For example, in the first line of the poem, the second syllable of the foot takes the emphasis:

When you | are old | and grey | and full | of sleep,

Overall, Yeats’s use of traditional, formal structure that deploys a highly recognizable meter signals to the reader that he is engaging with a tradition of more courtly love poems. However, as noted earlier, with the loss of the final couplet that would make this poem a sonnet, Yeats likewise signals that the love that is central to this poem has similarly been ‘cut short,’ as it flees from the beloved to the stars.