Primary

Primary may refer to:

• Primary (astronomy), the larger of two co-orbiting bodies
• Primary mirror, principal light-gathering surface of a reflecting telescope
• Primary (band), from Australia
• Primary circuit, electrical circuit in a transformer that receives current, as opposed to secondary circuit
• Primary election, an election by which a political party selects and nominates a candidate
• Power line, electric power transmission line fed to or from a transformer
• Primary (film), 1960 documentary
• Primary (LDS Church), children's Sunday School organization
• "Primary" (song), by The Cure
• Primary, the oldest period in the Geologic time scale (obsolete)
• "Primary", a song by Spoon from the album Telephono
• Primaries, remiges (wing feathers) in birds
• Primaries or primary beams, in E. E. Smith's science-fiction series Lensman
• The first stage in a thermonuclear explosive, may also be used alone in a lower-yield nuclear explosive, see nuclear weapon design