OUTDOOR and OUTDOORS?
Outdoor is an adjective used to mean something done, situated, or used out of doors:
We are planning a huge outdoors concert. ✖️
We are planning a huge outdoor concert. ✔️
Outdoors has the same meaning as outdoor but it is an adverb:
She likes to eat outdoor. ✖️
She likes to eat outdoors. ✔️
GAB