Mathwords O Oblate Spheroid Oblique Oblique Asymptote Oblique Cone Oblique Cylinder Oblique Prism Oblique Pyramid Obtuse Angle Obtuse Triangle Octagon Octahedron Octants Odd/Even Identities Odd Function Odd Number Odds Odds Against Odds in Favor Odds in Gambling Omega (Ω ω) Omicron (Ο ο) One Dimension One-Sided Limit One-to-One Function Open Interval Operations on Functions Opposite Reciprocal Order of a Differential Equation Ordered Pair Ordered Triple Ordinal Numbers Ordinary Differential Equation Ordinate Origin Orthocenter Orthogonal Outcome Outlier Oval Overdetermined System of Equations New TermsOrder of Operations (PEMDAS)Outlier Rule (1.5 x IQR)