Parallel (geometry)

Parallel (geometry)

Parallelism is a term in geometry that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not intersect or touch at a point are called parallel lines. Likewise, a line and a plane, or two planes, in three-dimensional Euclidean space that do not share a point are said to be parallel.

In a non-Euclidean space, parallel lines are those that intersect only in the limit at infinity.