plain sailing vs advance

plain sailing and advance both are nouns.

Word	Noun	Adjective	Verb	Adverb
plain sailing	Yes	No	No	No
advance	Yes	Yes	Yes	No

As nouns, advance is a hypernym of plain sailing; that is, advance is a word with a broader meaning than plain sailing:

Other hypernyms of plain sailing include advancement, forward motion, onward motion, procession, progress, progression.

plain sailing (noun)	advance (noun)
easy unobstructed progress	the act of moving forward (as toward a goal)
	increase in price or value
	a tentative suggestion designed to elicit the reactions of others
	a movement forward
	a change for the better; progress in development
	an amount paid before it is earned

plain sailing (adjective)	advance (adjective)
	being ahead of time or need
	situated ahead or going before

plain sailing (verb)	advance (verb)
	develop in a positive way
	rise in rate or price
	increase or raise
	develop further
	bring forward for consideration or acceptance
	obtain advantages, such as points, etc.
	move forward, also in the metaphorical sense
	cause to move forward
	move forward
	pay in advance
	give a promotion to or assign to a higher position
	contribute to the progress or growth of