A pentameter is a line of poem that has five metrical feet. The favored foot in English verse, where pentameter has been the dominant metre since the 16th century, is the iamb—ie, an unstressed syllable followed by a stressed one, represented in scansion as V'. While most languages have several possible ways to divide up the syllables in a word, English manages with just two: V and V'. There are rules about how many iambs should be used in a pentameter, but generally speaking, more is better. Many great poems are composed in pentameters, including "The Charge of the Light Brigade" and "Duty & Honor". Pentameters are common in speech too. For example, here's what Steve Martin says about pentameters: "They're easy to remember because it's made up of five feet: an iamb, a dactyl, a spondee, a spondee, an iamb." Finally, some words on iambic pentameter itself: It's based on the number 5. There are 20 lines in a traditional sonnet, and each line has 14 syllables (including the final couplet). That's 140 total syllables, which divides into 7 groups of 10 letters (each group represents a foot), so ideally you want to use five of each type of foot.