(biblical) The fifteenth book of the New Testament of the Bible, the first epistle to Timothy.

Abbreviation of 1 Timothy.

(topology, of a topological space) Having a singleton as its fundamental group.

A model railway gauge of 1.75 inches (44.45 mm).

(canoeing) A class of canoe for a single kneeling person.

(canoeing) A class of kayak for two seated people.

(video games) An item that grants the player an extra life in the game, staving off game over by one more try. / (video games) In a game with multiple players, an indicator or identifier of player 1.

The Garand semiautomatic rifle, also named the United States Rifle, Caliber .30, M1.

(initialism) Herpes simplex virus type 1, Human herpesvirus 1 in genus Simplexvirus.

plural of 1-up