vô tận 
endless, limitless, boundless, inexhaustible [ vô ] : (1) in-, im-, (negative prefix); (2) in, at, on; (3) to go into, enter [= vào]
[ tận ] : all the way; ending, finished; as far as, to
Most Common Compounds Set 1:
Most Common Compounds Set 2 :
vô tận