1. You asked "Is the word 'fellow' AN adjective IN this case?" Yes, 'fellow' is an adjective in this case. In fact, the phrase should be 'to treat fellow campers with respect' ( no 'the'). You would only use 'the' if this respect were specified in some way - for example 'to treat fellow campers with the respect they deserve'. 2. You asked "What synonyms COULD WE use instead OF ‘fellow’ here? You could use 'other' instead of 'fellow' here: 'to treat other campers with respect'. This is a simpler and less formal way of saying the same thing. I hope that these corrections and answers are useful.

Yes, fellow is the adjective here. However, "the respect" should be changed to "respect". You could also say "To treat other campers with respect".

An adjective.Fellow campers = other campers, team-mates, fellows, other tourists.