Euclidean distance is the intuitive notion of a 'straight-line' distance between two points in a Euclidean space.
Euclidian is an an adjective derived form the Name of Euclid. Euclid was a Greek mathematician living around 300 BC. He is known as the "founder of geometry".
Euclidian refers to many topics in geometry, e.g.
- Euclidian space
- Euclidian geometry
- Non-euclidian geometry
- Euclidian distance
- Euclidian ball
and in number theory, e.g.
- Euclidian division
- Euclidian algorithm
- Euclid's lemma
A Euclidian distance is the straight-line distance between two points in Euclidian space. Euclidian space is the conventional 2D or 3D (or for that matter $n$D) space that we usually use. It is also called flat space.
