course vs main course

course and main course both are nouns.

Word	Noun	Adjective	Verb	Adverb
course	Yes	No	Yes	Yes
main course	Yes	No	No	No

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

Other hyponyms of course include entree, appetiser, appetizer, starter, afters, dessert, sweet.

course (noun)	main course (noun)
a mode of action	a square mainsail
education imparted in a series of lessons or meetings	the principal dish of a meal
facility consisting of a circumscribed area of land or water laid out for a sport
(construction) a layer of masonry
part of a meal served at one time
a connected series of events or actions or developments
a body of students who are taught together
general line of orientation
a line or route along which something travels or moves

course (adverb)	main course (adverb)
as might be expected