In ancient Japan, a Kensei (剣聖) was a wandering warrior-monk who dedicated his entire existence to becoming the ultimate master of his chosen fighting style - usually a sword. The literal translation of "Kensei" is "sword saint". Thus, the term is synonymous with perfection, dedication, and lifelong learning.

The most famous Kensei is considered Miyamoto Musashi.

In some computer games (Shogun: Total War & Baldur's Gate II) and other circles you may find Kensei written as "Kensai". Actually it would work either way, since the word is merely an approximation to the Japanese pronunciation which in turn may differ depending on the accent or pronunciaton of the person using it. Variations like "Ken Sai", "Kansei", Kenshei", etc. are also perfectly possible and do exist. Also note that different languages based on the Roman alphabet (ie. French, German, etc.) pronounce letters different and might therefore choose different letters to simulate the Japanese sound.