(31) a. The faucet is leaking. I’ll call the plumber.
b. I’ve just finished one assignment. It’s a calculus assignment and and it’s very complicated.(Examples adapted from Finegan 2004:268)
In (31a), the noun phrase the plumber is definite (referring to a particular plumber) and new (introduced into the discourse for the first time). In (31b), the noun phrase a calculus assignment is indefinite (not referring to any specific calculus assignment) and given (previously mentioned in the discourse).