(mineralogy) The orthorhombic form of iron disulfide, FeS₂, occurring as yellow crystals. / (jewelry) Pyrite. / (historical) Any of various metal sulfides, usually iron sulfide minerals.

Notes in the margin of a document.

A female given name from French.

Of or pertaining to a traditional form of Mexican music, either sung or purely instrumental. / Of or pertaining to a band playing such music, or to the singers of such songs.

A traditional form of Mexican music, either sung or purely instrumental. / A group that plays mariachi music. / A member of such a group.

The wife of a marquess. / A woman holding the rank of marquess in her own right. / (slang, obsolete) An old-fashioned maid-of-all-work (female servant).

(military) A movement on foot by soldiers or prisoners of war, who must, in order to satisfy a military requirement, travel at a speed or in adverse conditions that would normally tire them excessively.

Any of the family Bibionidae of dark hairy flies. / Tipula hortulana (syn. Bibio hortulanus), now of family Tipulidae of crane flies.

The extra benefit received from a unit increase in the consumption of a good or service. It is calculated as the increase in total benefit divided by the increase in consumption.

(economics) The increase in cost that accompanies a unit increase in output; the partial derivative of the cost function with respect to output.