union vs nonunion

union is a noun but nonunion is not a noun.

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

union (noun)	nonunion (noun)
the act of making or becoming a single unit
the act of pairing a male and female for reproductive purposes
a device on a national flag emblematic of the union of two or more sovereignties (typically in the upper inner corner)
the occurrence of a uniting of separate parts
an organization of employees formed to bargain with the employer
a political unit formed from previously independent people or organizations
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)

union (adjective)	nonunion (adjective)
of trade unions	not belonging to or not allowing affiliation with a trade union