Free verse, a term coined by French poets of the early 20th century, from Vers Libre, is verse that does not follow any strict conventions of rhyme or meter. Whereas most poetic forms shape content around feet and rhyme, free verse is shaped around the content. Be aware not to confuse blank verse and free verse. While blank verse does not rhyme, it still has a regular meter.
Free verse is often thought to be a purely modern form of writing. However, examples of free verse poetry can be found in the Bible as well as in some medieval writings. This technique was most likely used to imitate the speech patterns of particular community groups.
The art of composing free verse is in shaping the poem around the composer's thoughts and ideas. Let's compare some lines that are shaped around meter and rhyme:
I wander thro' each charter'd street
Near where the charter'd Thames does flow,
And mark in every face I meet
Marks of weakness marks of woe.
William Blake, London at lines 1-4
Refer to audio file William Blake to hear how this should sound.
And the equivalent without:
I wandered through chartered streets
Along the banks of the chartered Thames, flowing through London
Every face I see,
Is marked with weakness and woe.
Notice that, in the first example, Blake has used a regular rhythm. Listen to the audio to hear this regular rhythm. In Example 2, notice the second line where the phrasing mirrors the actual flowing of the Thames.
As well as mirroring the thoughts of the poet, in each line the composer of free verse will also construct their poem in stanzas that are based on content rather than on convention. For example, in a sonnet a shift in thought occurs after the eighth line, in a ballad each stanza is four lines long. In free verse a stanza may be one line or it may be 20, depending on the composer's thoughts.
Take note, that poets who compose free verse often use meter in parts of their poems and still generally use standard language features, such as alliteration, assonance and imagery to make links between ideas and to express their thoughts as effectively as possible.
Consider the following animation When I heard the learn'd the astronomer for an sample analysis of a free verse poem.