Osculate

In mathematics, osculate, meaning to touch (from the Latin osculum meaning kiss), may refer to:

• osculant, an invariant of hypersurfaces
• osculating circle
• osculating curve
• osculating plane
• osculating orbit
• osculating sphere

The obsolete Quinarian system of biological classification attempted to group creatures into circles which could touch or overlap with adjacent circles, a phenomenon called 'osculation'.