Iamb

An iamb is a metrical unit. It occurs when two syllables are placed next to one another and the first is unstressed, or short, and the second is stressed, or long.

E.g. In the sentence, "The cat in the hat had a bat and a rat in his mat.," the stressed syllables occur in the bolded words, creating a pattern of unstressed-stressed syllables, which is a characteristic pattern of the iambic meter.

Iamb is the most common unit of meter in the English language and is often maintained throughout an entire poem.

 Examples: 

     I Wandered Lonely as a Cloud by William Wordsworth 

I wandered lonely as a cloud

That floats on high o’er dales and hills

    Because I could not stop for Death by Emily Dickinson 

Because I could not stop for Death –

He kindly stopped for me –