(trigonometry) A statement about the relationship between the tangents of two angles of a triangle and the lengths of the opposing sides.

(software engineering) The design principle that software should be conservative as to its own behaviour (i.e. strictly compliant with specifications) but liberal in the behaviour it tolerates from other systems.

The rule that the best video games are easy to learn but difficult to master.

(phonology) A sound change and a synchronic phonological rule that operated during an early stage of the Proto-Indo-European language. The rule deleted coda fricatives *s or laryngeals *h₁, *h₂ or *h₃ (cover symbol *H), with compensatory lengthening occurring in a word-final position.

Alternative form of Charles's law

(economics) A principle whereby those who produce anything must be paid sufficiently to buy the products they make, whether it be in a local economy or the world economy.

plural of aunt-in-law

(nonstandard) The wife of one's uncle or aunt (parent's sibling). / The aunt of one's husband. / The aunt of one's wife.

The observation that a person can expect to experience an event with odds of one in a million approximately once per month.

(archaic) Brothers-in-law