The following expressions originate from Japanese swordsmanship but apply to kumite also.
KEN NO SEN - Seizing the initiative. To move in quick and strong, attacking first before opponent is ready.
GO NO SEN - Allowing the opponent to attack first defending and then countering.
SEN NO SEN - Attacking at the exact moment as the opponent to seize the initiative. Involves a simultaneous block and strike (performed in one count).
SEN SEN NO SEN - Pre-empt the opponent attack by striking a split second earlier.
YU NO SEN - Testing the opponent defences by shifting and changing position, catching him wrong footed in order to create an opening and then attacking.
TAI NO SEN - Allowing the opponent to attack first, drawing him in by presenting a target, defending against the expected attack and countering quickly.
Courtesy of SEKU