Blank verse is a poetic form consisting of unrhymed iambic pentameter. 

• Iambic pentameter refers to the rhythm, or meter, the words in a line make, and this rhythm is measured in groups of syllables called “feet,” with iambic referring to the type of foot used. 
• Pentameter means a line of five iambs, or feet. 

Blank verse is considered the verse form that most closely matches the patterns of English speech, making it ideal for poetic verse written in English. Blank verse was first introduced in the 16th century by Henry Howard, Earl of Surrey. The form was adopted by many English Renaissance writers, including Christopher Marlowe and William Shakespeare.

The first three lines of Robert Frost’s poem “Mending Wall” demonstrate blank verse:

Something there is that doesn’t love a wall,

That sends the frozen-ground-swell under it,

And spills the upper boulders in the sun;

B. Yeats’s poem “The Second Coming” is another example of blank verse: 

Turning and turning in the widening gyre

The falcon cannot hear the falconer;

Things fall apart; the center cannot hold;

Mere anarchy is loosed upon the world,

Shakespeare made extensive use of iambic pentameter throughout his plays, but he also included moments of blank verse, which allowed for moments that seemed more colloquial in tone. For example, in A Midsummer Night’s Dream, Theseus’s speech to Hippolyta is written in blank verse:

The poet’s eye, in a fine frenzy rolling,

Doth glance from heaven to earth,

from earth to heaven;

And, as imagination bodies forth

The forms of things unknown, the poet’s pen

Turns them to shapes and gives to airy nothing

A local habitation and a name.

(act 5, scene 1: lines 12–17)