figure of eight vs figure 8

figure of eight and figure 8 both are nouns.

Word	Noun	Adjective	Verb	Adverb
figure of eight	Yes	No	No	No
figure 8	Yes	No	No	No

As nouns, figure of eight and figure 8 are synonyms defined as:

figure of eight and figure 8: a two-dimensional figure having the shape of the number eight

Other synonyms of figure of eight include figure eight.

figure of eight (noun)	figure 8 (noun)
a knot having the shape of the numeral 8; tied in a rope that has been passed through a hole or pulley and that prevents the rope from coming loose	a two-dimensional figure having the shape of the number eight
a two-dimensional figure having the shape of the number eight