WordNet records no synonym and no antonym for canopy. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
the transparent covering of an aircraft cockpit
the umbrellalike part of a parachute that fills with air
a covering (usually of cloth) that serves as a roof to shelter an area from the weather
Synonyms, antonyms and the broader and narrower relations for canopy come from Princeton University’s WordNet. Full sources and licences.