to sing louder. / (music) to sing higher, to sing an ascending scale

plural of sine wave

Having one strand

(historical) A duel between single representatives of opposing armies, with the outcome accepted as the battle's outcome.

plural of single combat

A room that has one single bed.

(astrophysics) An as yet theoretical gravitational singularity with no event horizon, making it observable, unlike a black hole whose event horizon prevents light from reaching an observer situated outside the event horizon.

(derogatory) a person with mediocre or amateur singing capabilities.

(physics) A location where the quantities that are used to measure the gravitational field become infinite in a way that does not depend on the coordinate system.

Used to ask whether the interlocutor does or doesn't have a (romantic) partner.