Blank verse is unrhymed iambic pentameter. An iamb is a metrical foot consisting of one short (or unstressed) syllable followed by one long (or stressed) syllable. Pentameter means there are five of those in a line. You most likely known the sound of blank verse and don’t even know it. Recognize this?
But, soft! what light through yonder window breaks?
It is the east, and Juliet is the sun…
