copula
noun /ˈkɒpjələ/
/ˈkɑːpjələ/
(also linking verb)
(grammar- a verb such as be or become that connects a subject with the adjective or noun (called the complement) that describes it
系词;连系动词 词源early 17th cent.: from Latin, ‘connection, linking of words’, from co- ‘together’ + apere ‘fasten’.