A strike is an unarmed attack with hand, arm or elbow in order to cause harm to an opponent. An attack with the hand closed into a fist is often called a punch. A strike with a foot or leg is called a kick. Strikes are usually a bit weaker than kicks, but faster to deliver.
Strikes are employed in many martial arts, notably boxing and muay thai. Few martial arts employ no strikes at all, wrestling is one of them. In most arts, strikes are complemented by kicks and grappling.
Strike is the generic name for a blunt, crushing attack made with or without a weapon. Striking weapons inclide the club, the mace and the warhammer and is probably the oldest category of weapons known to humans.
A strike is a deliberate absence from work. This is a means often emloyed by labor unions in order to change the conditions of work set up by the employer. Strikes first became important during the industrial revolution, when mass labour became important in factories and mines.
A military strike is a limited attack on a specified target. Strikes are used, amongst other things, to render facilities inoperable, to asssassinate enemy leaders and to limit supply to enemy troops. An air strike is a military strike made using explosives delivered from an aircraft, often a bomber.