towel bar vs towel rail

towel bar and towel rail both are nouns.

Word	Noun	Adjective	Verb	Adverb
towel bar	Yes	No	No	No
towel rail	Yes	No	No	No

As nouns, towel bar and towel rail are synonyms defined as:

towel bar and towel rail: a horizontal bar a few inches from a wall for holding towels

towel bar (noun)	towel rail (noun)
a horizontal bar a few inches from a wall for holding towels	a horizontal bar a few inches from a wall for holding towels