Crossword puzzle clue "formed a curve"

ARC, to make an electric discharge

ARCH, to bend like a curved structure

a curve of the kind formed by a uniform chain hanging freely from two points not in the same vertical line

to form oval openings

ACE, to serve an unreturnable shot e.g. in tennis

ACNODE, an isolated point not upon a curve, but whose coordinates satisfy the equation of the curve so that it is considered as belonging to the curve

further on