Porson's Law

Porson's Law is a metrical law concerning bridge. It states that, in anceps-cretic or cretic-anceps meters, such as the iambic trimeter, no word-break may follow a long anceps, except in the case of a main caesura.

This metrical law (which was later named after its creator)appeared originally in Porson's edition of Hecuba of Euripides. It's original phrasing was :" Nempe hanc regulam plerumque in senariis observabant Tragici, ut, si voce que Creticum pedem efficeret terminaretur versus, eamque vocem hypermonosyllabon praecederet, quintus pes iambus vel tribrachys esse deberet". In translation:" That is to say, the tragic poets followed this law most frequently in verses consisting of six feet (i.e. iambic trimeters). If a verse ends with a cretic metre and this metre is preceded by a word of more than one syllables, then the fifth foot of this verse must be either an iambus or a tribrachys".

Regarding iambic trimeter, Martin West defined Porson's Law as "when the anceps of the third metron is occupied by a long syllable, this syllable and the one following belong to the same word, unless one of them is a monosyllable." Accordingly, after a short anceps in the third metron, the beginning of a new word is avoided. Further he observed about the generality of the Law that "there are very few exceptions in tragedy, most of them textually suspect."

References

• M. L. West, Introduction to Greek Metre (Oxford 1987) page 25.