Oct

• OCT, the professional designation granted to certified teachers in Ontario
• Octal, the numeral system
• Octans, a constellation
• Optical coherence tomography, an interferometric three dimensional imaging method used in (e.g.) ophthalmology
• Optimal cutting temperature compound or O.C.T., for embedding tissues to be cryosectioned
• Organic Cation Transporter
• Orion Correlation Theory, a pseudoarchaeological explanation for the groundplan layout of the pyramids at Giza, advanced by writers such as Robert Bauval, Graham Hancock and Adrian Gilbert
• Ornithine Carbamoyltransferase Deficiency
• Overseas Chinese Town, a theme park in Shenzhen, China
• Overseas countries and territories, twenty territories that have a special relationship with one of the member states of the EU
• Oxford Classical Texts
• Oxytocin challenge test
• Oct, a fictional species from the the Culture series
• Octahedron