metrical

Metrical is an adjective relating to meter in poetry, prosody, and versification. It describes the systematic arrangement of rhythm in verse through patterns of stressed and unstressed syllables. The basic unit is the foot, a small combination of syllables, of which common types include the iamb (unstressed-stressed), the trochee (stressed-unstressed), the anapest (unstressed-unstressed-stressed), the dactyl (stressed-unstressed-unstressed), and the spondee (two stressed). A line may be described by its meter, that is, by the sequence and number of feet it contains. When a line uses five iambs, it is called iambic pentameter, a staple of English verse; other well-known forms include pentameter, tetrameter, and trimeter.

Scansion is the practice of marking a line to show its metrical pattern and rhythm, often using marks for stressed and unstressed syllables. Poets may follow a strict meter or vary it for effect; feminine endings (an extra unstressed syllable) and occasional metrical substitutions are common features in metrical verse. In contrast, free verse uses irregular or no consistent meter.

Historically, metrical systems differ by language. Classical Greek and Latin poetry relied on quantitative meter, based on syllable length, while English and many other languages favor stress-based meters. The term metrical is therefore used primarily in discussing poetry and prosody to describe and analyze the rhythm and structure of verse.