The translation of maai is: space. The definition of Maai: Proper distancing or timing with respect to one’s partner in a kendo match. In kendo there are three distance catagories: Chikama or close distance, Issoku itto no maai or one step distance and toma or far distance. Issoku Itto no maai or one step distance is the preferred distance because you can see the opponents whole body easily. Toma distance is the generally to far to strike from and few kendoka are able to hit from toma in one step.
With practice you will find your comfort hitting distance which may be the same or different for your oppenents. Maai is not a static distance it is always changing from moment to moment, often it is a transition from far to close and back again. Maintaining a maai position is an advanced level kendo so it takes time to develop. Practice maai so that it is second nature and not a conscious effort to dominate your opponent by keeping just out of reach of your opponents strikes yet within easy reach of your strikes. Another dimension of maai is to control “space.” Controlling Space around you is very important when fighting multiple opponents, keeping the space to your advantage. Controlling Space also infers the ability to read and control time (reaction distance from opponent) time in the fractions of a second it takes an opponent to strike from what ever distance (maai) he is at any given moment. A faster opponent will travel the same maai striking distance faster than a slow opponent covering the same maai striking distance. Adjust for slower and faster opponents, avoiding the faster opponents maai striking distance until you are ready to strike and or shorten your kokoro no maai when in striking distance.
Kokoro no maai is the term used to describe a distance in which both opponents can easily strike from, yet the opponent can not strike because of an awareness lapse. The term kokoro means heart or spirit, in this context describes an opponent that has a spirit at rest or sleeping. An awareness lapse can be used to your advantage (giving you time and suki) sensing the opponents state of mind, sensing the awareness or lack of awareness of your opponent.