copula
noun [ C ] language specialized uk/ˈkɒp.jə.lə/ us/ˈkɑː.pjə.lə/
系（动）词
a type of verb, of which the most common is "be", that joins the subject of the verb with a complement
In the sentence "You smell nice", "smell" is a copula. 在 You smell nice 这句话中，smell 是系动词。
Synonym: linking verb