call of OnTriggerEnter

I create a function OnTriggerEnter(Collider other). How can I call it in Update()?

You shouldn't. OnTriggerEnter is supposed to be called by the game engine automatically when a trigger collision occurs

I know it. But for some reason a function is called only one time. and function works only then, when at a start one object with touches with other. do not you know the decision of this problem?

P.S. I am sorry my English, he is not very much good.

I understood that a function was not called, when objects begin to move. Does anybody know in what reason?

You should try with OnTriggerStay.