In prosody the Inversion of a foot

Foot (prosody)

The foot is the basic metrical unit that generates a line of verse in most Western traditions of poetry, including English accentual-syllabic verse and the quantitative meter of classical ancient Greek and Latin poetry. The unit is composed of syllables, the number of which is limited, with a few...

, or anaclasis, is the reversal of the order of its elements. For example, in English Accentual-syllabic verse

Accentual-syllabic verse

Accentual-syllabic verse is an extension of accentual verse which fixes both the number of stresses and syllables within a line or stanza. Accentual-syllabic verse is highly regular and therefore easily scannable...

 the most common inversion by far is the reversal of the first iamb in a line of verse, thus resulting in a trochee

Trochee

A trochee or choree, choreus, is a metrical foot used in formal poetry consisting of a stressed syllable followed by an unstressed one...

. Examples can be found in the first and second lines of Hamlet

Hamlet

The Tragical History of Hamlet, Prince of Denmark, or more simply Hamlet, is a tragedy by William Shakespeare, believed to have been written between 1599 and 1601...

's soliloquy:

To be, or not to be: that is the question:

Whether 'tis nobler in the mind to suffer

The slings and arrows of outrageous fortune'

Here, that is emphasized rather than is, which would be a wrenched, or unnatural accent. The first syllable of Whether is also stressed, making it a trochaic beginning.