antecedent

Relative clauses need something such as nouns to refer to, and the relationship ought to be clear. Avoid constructions like these where the antecedents (words or phrases that subsequent material refers to) are either absent or unclear: I'd sign up for advanced calculus if I were smart, which I'm not. The clause which I'm not has no antecedent; also, if I were smart already tells the reader that I am not smart. Don't try to make an entire clause an antecedent for a relative clause, as in I need to purchase an entirely new computer system, which upsets me. Say instead I need to purchase an entirely new computer system, and this [or that] upsets me. Similarly, avoid relative clause constructions with vague antecedents: She crashed the ultralight aircraft into the freeway, which was her own fault. Since the freeway was definitely not her own fault but the crash indeed was, reword the sentence: Crashing the ultralight aircraft into the freeway was her own fault or She crashed the ultralight aircraft into the freeway in an accident that was her own fault.