Rhythm

Definition: Patterns of stressed and unstressed syllables. Measured in feet.

Example: 

A chimney, breathing a little smoke.
The sun, I can't see
making a bit of pink
I can't quite see in the blue.
The pink of five tulips
at five P.M. on the day before March first.
                                 -From "February" by James Schuyler



Significance: It is like a "beat" in poetry. When the speaker reads the poem, it gives a flow to the speaker.