All eight stanzas in “Ode to a Nightingale” share the same rhyme scheme: ABABCDECDE. Students of the sonnet will immediately recognize familiar elements in this scheme, which integrates distinct rhyme patterns from the English and Italian sonnet forms. Recall that an English sonnet consists of three quatrains followed by a final couplet. Quatrains in the English sonnet use an alternating rhyme scheme that’s identical to the quatrain that opens each of Keats’s stanzas: ABAB. But instead of following this with another quatrain, Keats inserts a rhyming pattern that resembles the final sestet of an Italian sonnet, which typically rhymes as follows: CDECDE. Though “Ode to a Nightingale” isn’t a sonnet, Keats showcases his formidable skill in the way he condenses the sonnet form into a ten-line stanza and then proceeds to write a series of eight such stanzas. In other words, he at once to condenses and expands on the sonnet form, of which he had elsewhere already shown himself to be a master.

As for the rhymes themselves, they are all exact and take a so-called masculine form, meaning that they occur on the final stressed syllable of each line. There is nothing particularly notable about these aspects of the poem’s rhymes. What is notable, however, is the way Keats frequently forms rhymes with polysyllabic words. For the most part, the rhyme words in the poem are monosyllabic. This is particularly true in the case of the rhymes that form the quatrain at the beginning of each stanza. Consider the rhyme words for the first four lines: “pains,” “drunk,” “drains,” and “sunk.” By contrast, in the sestet that concludes each stanza, Keats almost always features at least one polysyllabic word in a rhyming position. Here’s the sestet from the first stanza (lines 5–10):

     'Tis not through envy of thy happy lot,
              But being too happy in thine happiness,—
                     That thou, light-winged Dryad of the trees
                             In some melodious plot
              Of beechen green, and shadows numberless,
                     Singest of summer in full-throated ease.

Whereas the pairs “lot”/“plot” and “trees”/“ease” both feature monosyllables, Keats also forms a rhyme pair based on two different trisyllabic words: “happiness” and “numberless.” Similarly striking pairs appear in subsequent sestets—for example, “Hippocrene” and “unseen” (lines 16 and 19), as well as “eglantine” and “dewy wine” (lines 46 and 49). These polysyllabic rhymes bring interesting variety to what is otherwise a very repetitive rhyme scheme.