A metron /ˈmɛtrɒn/, /ˈmɛtrən/ (from ancient Greek μέτρον "measure"), plural metra, is a repeating section, 3 to 6 syllables long, of a poetic metre.
The word is particularly used in reference to ancient Greek. According to a definition by Paul Maas, usually a metron consists of two long elements and up to two other elements which can be short, anceps or biceps. Thus an iambic metron is x – ᴗ – (where "x" represents an anceps element), a trochaic metron is – ᴗ – x, an ionic metron is ᴗ ᴗ – –, an anapaestic metron is ᴗᴗ – ᴗᴗ –, a cretic metron – ᴗ –, a baccheus is ᴗ – –, and a spondee is – –.