OP

OP, O.P., or Op may refer to any of the following:

• Observation post, a position from which soldiers can watch enemy movements
• Ocean Pacific, a retail company based in California, United States
• Orange pekoe, a grade of black teas
• Ordo Praedicatorum, a Catholic religious order
• Operating profit, a measure of business profitability
• Out of print, a status of a book title at a publishing house
• Op, or grow-op, a marijuana growing operation
• Open pollination

Mathematics

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

Culture

• Op art, 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, stage right on a theatre stage
• Op., an abbreviation for Opus number, used to denote one work of musical composition from many
• Optimus Prime (Transformers), a character from the Transformers franchise
• One Piece, a Japanese manga and anime
• A shortening for opening credits, especially in anime fandom

Internet and gaming

• Original post or original poster, the first post or person to post on a topic in an online forum
• Overpowered, in video games, noting that a particular aspect or character is unbalanced and thereby too strong
• An Internet Relay Chat operator

Education

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

Geography

• Oak Park, Illinois
• Oakland Park, Florida
• Orchard Park, New York
• Overland Park, Kansas
• Ohio Penitentiary, a now-demolished prison

Science and medicine

• The 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
• A surgical operation