OP or Op may refer to:

• Observation post, a position from which soldiers can watch enemy movements
• Ocean Pacific, a retail company based in California, USA
• Orange pekoe, a term used in the Western tea trade to describe a particular grade of black teas
• Orange peel, the outer layer of an orange fruit
• Ordo Praedicatorum, members of the Dominican Order
• Operating Procedure, a standardised working protocol

Mathematics

• Operator, in mathematics, a mapping from one vector space or module to another
• Op (statistics), a symbol used in probability mathematics
• Octagonal prism, is a prism formed by square sides and two regular octagon caps

Culture

• Op art, also known as optical art, is a style of visual art that makes use of optical illusions
• Op-ed, a newspaper opinion piece of a writer unaffiliated with the editorial board
• Opposite prompt, the right side of a theatre stage
• Opus number, used to donate one work of musical composition from many
• Optimus Prime, a character from the Transformers franchise
• One Piece, a Japanese manga and anime created by Eiichiro Oda
• Ordo Praedicatorum ("Order of Preachers"), a Catholic order founded by Saint Dominic in 1216
• "Original Post", in an E-mail discussion thread

Computing

• Office Practicum, an electronic medical record (EMR) keeping software suite created by Connexin Software, geared toward pediatric medical practices
• Original poster, a term used on online forums to denote the first poster
• Overpowered, a term used to note that one team in a game is stronger than another
• Overpriced, a term used mostly on online games to note about an item that is being marketed for a price higher than normal
• A channel operator on an Internet Relay Chat
• OpenID Provider
• Overlord Protocol

Education

• Oratory Preparatory School, a Catholic preparatory day school for boys in New Jersey, USA
• Overall Position, the grade appointed to Queensland high-school graduates
• Old Persean, an ex-pupil of the Perse School, Cambridge Old Perseans
• Old Pauline, an ex-pupil of St Paul's School, London

Geography

• Oak Park, Illinois, a village west of Chicago, USA
• Oakland_Park,_Florida, a city in the Fort Lauderdale Metropolian Area
• Orchard Park, New York, a town south of Buffalo, New York
• Overland Park, Kansas, a city in the Kansas City Metropolitan Area

Science and medicine

• Oropharyngeal airway, leading from the mouth to the pharynx
• Organophosphate, the general name for esters of phosphoric acid
• Osteitis pubis, a medical condition which is prevalent among players of Australian rules football
• Osteoporosis, a degenerative disease of the bones that leads to an increased risk of fracture
• Short-hand slang for a surgical operation

Noun

op n. (plural opuri)

1. (archaic) need, necessity

• nevoie, necesitate