In English, the most prevalent foot are the iamb, trochee, dactyl, and anapest. Two feet are merged into a bigger unit termed a metron (pl. metra) or dipody in various types of metre, such as the Greek iambic trimeter. A foot is a discrete unit of language used for syllabication rather than as part of a word. Of these, the iamb is by far the most common, appearing in almost every line of English poetry. The other three feet appear only occasionally. An iamb is any verse line composed of one unstressed syllable followed by one stressed syllable, as in love and labor's two things never mixed. A trochaic line has a strong stress on the first syllable and a weak stress on the second, as in proud and high. A dactylic line has a strong stress on both its syllables, as in fly and cry. An anapestic line contains the same number of syllables as anapaests, which are lines ending with a half-syllable that is not pronounced, as in moonless night. Iambic pentameter is the most common type of metre in English poetry. It is composed of five pairs of metrically identical iambic feet, each pair separated by a spondee: love and labor, life and death, heaven and hell, etc.