canvas vs big top

canvas and big top both are nouns.

Word	Noun	Adjective	Verb	Adverb
canvas	Yes	No	Yes	No
big top	Yes	No	No	No

As nouns, big top is a hyponym of canvas; that is, big top is a word with a more specific, narrower meaning than canvas:

Other hyponyms of canvas include circus tent, round top, top, field tent, Sibley tent, wall tent.

canvas (noun)	big top (noun)
a heavy, closely woven fabric	a canvas tent to house the audience at a circus performance
the mat that forms the floor of the ring in which boxers or professional wrestlers compete
a tent made of canvas fabric
a large piece of fabric (usually canvas fabric) by means of which wind is used to propel a sailing vessel
an oil painting on canvas fabric
the setting for a narrative or fictional or dramatic account

canvas (verb)	big top (verb)
cover with canvas