granny vs reef knot

granny and reef knot both are nouns.

Word	Noun	Adjective	Verb	Adverb
granny	Yes	No	No	No
reef knot	Yes	No	No	No

As nouns, reef knot is a hypernym of granny; that is, reef knot is a word with a broader meaning than granny:

Other hypernyms of granny include flat knot.

granny (noun)	reef knot (noun)
a reef knot crossed the wrong way and therefore insecure	a square knot used in a reef line
the mother of your father or mother
an old woman