Coordination exhibits unusual syntactic properties: the conjuncts need not be identical but they must obey some parallelism constraints, and their number is not limited.
Romance languages have conjunctive (‘and’), disjunctive (‘or’), adversative (‘but’), and negative (‘nor’) conjunctions, some of which have a correlative use, such as (French) soit . . . soit, (Italian, Spanish) o . . . o, (Portuguese) quer . . . quer, (Romanian) sau . . . sau (‘either . . . or’). They allow coordination of clauses and phrases but also of words (French: le ou la secrétaire ‘the.m.sg or the.f.sg secretary’) and even some word parts (Italian: pre- o post-moderno ‘pre- or post-modern’).
Romance languages show intricate agreement patterns in case of coordination. For number agreement, disjunctive coordination allows for total or partial agreement (Paul ou Marie viendra/viendront. ‘Paul or Mary come.fut.sg/pl’). For gender agreement, conjunctive coordination obeys gender resolution (French: un garçon et une fille gentils ‘a boy.m.sg and a girl.f.sg nice. m.pl’) or closest conjunct agreement (Spanish: El idioma y literatura rusa ‘the language.m.sg and litterature.f.sg Russian.f.sg’).
Coordination may also involve nonconstituents (Italian: Darò un libro a Giovanni e un disco a Maria. ‘I’ll give a book to Giovanni and a record to Maria’) and ellipsis, such as gapping (French: Paul arrive demain et Marie aujourd’hui. ‘Paul arrives tomorrow and Mary today’), with possible mismatches between the elided material and its overt antecedent.