What literary device is described as the leaving out of an unstressed syllable or vowel to keep a regular meter?

Elision is a literary device that involves omitting a syllable or a vowel, typically an unstressed one, to maintain the rhythm or meter of a line of poetry. This technique allows poets to create a smoother flow or to fit their words into a specific metrical pattern without altering the overall meaning of the text. By removing certain sounds, poets can ensure that the rhythm remains consistent and aligns with the established meter, making their verse more musical and structured.

The other options do not pertain to this specific function. Alliteration refers to the repetition of initial consonant sounds in close proximity, which contributes to the sound and musical qualities of language but does not involve the omission of syllables. Assonance focuses on the repetition of vowel sounds within words, creating internal rhyming effects without skipping syllables. Consonance is similar to alliteration but involves the repetition of consonant sounds anywhere in the words, which also does not include the act of leaving out syllables to fit a meter.