figure 8 vs figure of eight

figure 8 and figure of eight both are nouns.

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

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

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

Other synonyms of figure 8 include figure eight.

figure 8 (noun)	figure of eight (noun)
a two-dimensional figure having the shape of the number eight	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