outside vs outdoors

outside and outdoors both are nouns.

Word	Noun	Adjective	Verb	Adverb
outside	Yes	Yes	No	Yes
outdoors	Yes	No	No	Yes

As nouns, outdoors is a hyponym of outside; that is, outdoors is a word with a more specific, narrower meaning than outside:

Other hyponyms of outside include open, open air, out-of-doors.

As adverbs, outside and outdoors are synonyms defined as:

Other synonyms of outside include alfresco, out of doors.

outside (noun)	outdoors (noun)
the outer side or surface of something	where the air is unconfined
the region that is outside of something

outside (adjective)	outdoors (adjective)
relating to or being on or near the outer side or limit
located, suited for, or taking place in the open air
leading to or from the outside
originating or belonging beyond some bounds
functioning outside the boundaries or precincts of an organized unit
coming from the outside
from or between other countries
(of a baseball pitch) on the far side of home plate from the batter
on or toward an outer edge
unlikely to occur

outside (adverb)	outdoors (adverb)
outside a building	outside a building
on the outside