(games) A rule used in certain strategy games for the purpose of fairness, where immediately after the first player's initial move the opposing player may optionally switch, taking over the first player's role and position for the rest of the game.

plural of pie rule

(linguistics, phonology, Indo-European studies) A rule of the Proto-Indo-European reconstructed language that states that a labiovelar stop (*kʷ, *gʷ, *gʷʰ) dissimilates to an ordinary velar stop (*k, *g, *gʰ) next to the vowel *u or its corresponding glide *w.

An observation about the early stage of speciation, stating that if in a species hybrid only one sex is inviable or sterile, that sex is more likely to be the heterogametic sex.

plural of lesbian rule

(transitive) To draw a line underneath, for example to mark the end of a topic or of an accounting period.

plural of rule of engagement

(military, law enforcement, chiefly in the plural) An internal rule among a military, police, etc. force defining the circumstances in which and manner with which to use force.

plural of mercy rule

plural of preliminary ruling