fusion vs union

fusion and union both are nouns.

Word	Noun	Adjective	Verb	Adverb
fusion	Yes	No	No	No
union	Yes	Yes	No	No

As nouns, union is a hypernym of fusion; that is, union is a word with a broader meaning than fusion:

As nouns, union is a hypernym of fusion; that is, union is a word with a broader meaning than fusion:

Other hypernyms of fusion include unification.

fusion (noun)	union (noun)
the act of fusing (or melting) together	the act of making or becoming a single unit
correction of an unstable part of the spine by joining two or more vertebrae; usually done surgically but sometimes done by traction or immobilization	the act of pairing a male and female for reproductive purposes
the combining of images from the two eyes to form a single visual percept	a device on a national flag emblematic of the union of two or more sovereignties (typically in the upper inner corner)
an occurrence that involves the production of a union	the occurrence of a uniting of separate parts
a nuclear reaction in which nuclei combine to form more massive nuclei with the simultaneous release of energy	an organization of employees formed to bargain with the employer
the merging of adjacent sounds or syllables or words	a political unit formed from previously independent people or organizations
the state of being combined into one body	a set containing all and only the members of two or more given sets
	healing process involving the growing together of the edges of a wound or the growing together of broken bones
	the state of being joined or united or linked
	the state of being a married couple voluntarily joined for life (or until divorce)

fusion (adjective)	union (adjective)
	of trade unions