This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

In grammar and logic, relating to or of the nature of a copula.

adj. of or relating to a copula

"In the Oxford English Grammar, Sidney Greenbaum writes: "If the copular verb is BE and if the subject predicative identifies the subject, the subject and subject predicative can change places.""