..The poem alternates between iambic dimeter and iambic tetrameter. Iambic dimeter is a metric pattern with two pairs of syllables per line, the first syllable of each pair unstressed and the second one stressed. A pair of syllables with this pattern is called an iamb. Iambic tetrameter is a metric pattern with four pairs of syllables per line, all of them iambs. For further information about iambic dimeter and iambic tetrameter, seeMeter.
The following example demonstrates the metric pattern.