Interception is the preferred method of defense. Interceptions occur on intention (before the attack), on initiation (as the attack starts), or during execution (as attack is in progress), whereas blocks are used as the attack is about to make contact. Interception on intention is the best option but it requires a skilled fighter who may anticipate attacks by "reading" an opponent's non-verbal clues.
Ways to intercept an attack:
Using upper body. Most common interception tool is the jab. It draws opponent's attention away from the intended attack, causes the opponent have to think about defense, and it may make contact, which further makes the opponent reconsider an attack.
Using lower body. Most common interception tools are the leading/trailing side kick, leading/trailing front kick, leading/trailing twist kick, or any kick used to stop the forward motion of an attacker.
At some point between initiation of an attack and your having to block it, evasion comes into play. Evasion is simply avoiding an attack. Evasion is highly efficient since no contact occurs with the opponent. Evasive movements may involve footwork (such as sidesteps or stepping backward) or just body movement (such as the duck, slip, or bob and weave).
To evade you must be able to change the direction of any part of your body with the smallest impetus and with no conscious thought or physical restriction. This requires you to be relaxed, reactive, rooted, and yielding. Humans think! When being attacked, this split second of thought, and possible indecision, causes a split second of body tension and non-movement. Animals do not need make a moral or strategic choices when challenged; they simply either fight or run.