fin de siecle vs ending

fin de siecle and ending both are nouns.

Word	Noun	Adjective	Verb	Adverb
fin de siecle	Yes	Yes	No	No
ending	Yes	No	No	No

As nouns, ending is a hypernym of fin de siecle; that is, ending is a word with a broader meaning than fin de siecle:

Other hypernyms of fin de siecle include end.

fin de siecle (noun)	ending (noun)
the end of a century, especially the 19th century	the act of ending something
	the end of a word (a suffix or inflectional ending or final morpheme)
	the last section of a communication
	event whose occurrence ends something
	the point in time at which something ends

fin de siecle (adjective)	ending (adjective)
relating to or characteristic of the end of a century (especially the end of the 19th century)