Free Verse
Free verse is unrhymed poetry with lines of varying lengths, and containing no specific metrical pattern.

The poetry of Walt Whitman provides us with many examples.

Note the poem from Walt Whitman:

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When I Heard the Learn'd Astronomer
Walt Whitman

When I heard the learn'd astronomer,
When the proofs, the figures, were ranged in columns before me,
When I was shown the charts and diagrams, to add, divide, and measure them,
When I sitting heard the astronomer where he lectured with much applause in the lecture-room,
How soon unaccountable I became tired and sick,
Till rising and gliding out I wander'd off by myself,
In the mystical moist night-air, and from time to time,
Look'd up in perfect silence at the stars.