Caesura
A deliberate pause or break within a line of poetry.
A caesura interrupts a line partway through, often marked by punctuation, creating a beat of silence in the middle of the verse. Writers use it to control pacing, mimic natural speech, or split a line into contrasting halves. In older verse it falls at a fixed point; in modern poetry it moves freely for effect.
Example
Each line pauses in the middle, splitting it into two balanced parts, a structural caesura that gives the old poem its steady, hammering rhythm.
Beowulf · Anonymous (Old English poet)