sewing vs stitch

sewing and stitch both are nouns.

Word	Noun	Adjective	Verb	Adverb
sewing	Yes	No	No	No
stitch	Yes	No	Yes	No

As nouns, stitch is a hyponym of sewing; that is, stitch is a word with a more specific, narrower meaning than sewing:

sewing: needlework on which you are working with needle and thread
stitch: a link or loop or knot made by an implement in knitting, crocheting, embroidery, or sewing

Other hyponyms of sewing include applique, binding, gather, gathering, darn, mend, patch, patchwork.

sewing (noun)	stitch (noun)
joining or attaching by stitches	a link or loop or knot made by an implement in knitting, crocheting, embroidery, or sewing
needlework on which you are working with needle and thread	a sharp spasm of pain in the side resulting from running

sewing (verb)	stitch (verb)
	fasten by sewing; do needlework