Cases of word usage

1) a way under an arch (archway)

2) an arch of hair about the eye (brow)

3) to have a vague feeling, idea, that; to make something into the shape of an arch (hunch)

4) a stone at the top of an arch locking the others into position; the central principle on which an argument, idea etc depends (keystone)

5) the distance between the tips of a person's thumb and little finger when stretched out; the distance or pat between the supports of an arch or bridge; a length in time, from beginning to end (span)