A volleyball hit could be legal or illegal hit but it depends on several circumstances. I just want to add up a basic example in my answer: a team can only hit the ball three times before it must go over the net to the opponent's side. A fourth hit is illegal. Well if a block didn’t constitute a hit, in that particular circumstances a team can block up a shot and can continue forward to hit it three more consecutive times.
A player is not allowed to use his open palms beneath the ball to hit it. A player is even restricted to throw the ball with open hand neither you are allowed to throw the ball as it will be considered as an illegal hit. There are double hits too which are legal only when team first contracts,at times of service but the double hits are considered as illegal on subsequent hits
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