When To Use Then and Than
What to Know
Than and then are different words. Than is used in comparisons as a conjunction, as in "she is younger than I am," and as a preposition, "he is taller than me." Then indicates time. It is used as an adverb, "I lived in Idaho then," noun, "we'll have to wait until then," and adjective, "the then governor."
There's nothing more embarrassing then correcting someone's language only to realize that your correction contains its own error. Like maybe the one in our first sentence. Did you see it? That harmless little four-letter word then. It should have been than.
People get tripped up on then and than all the time—and why not? They look and sound so similar, and both words function as linguistic workhorses—then is most often an adverb, while than is usually a conjunction—which means that we mostly use them to connect more obviously significant nouns, verbs, and adjectives.
The way to keep the pair straight is to focus on this basic difference: than is used when you're talking about comparisons; then is used when you're talking about something relating to time.
Than is the word to choose in phrases like smaller than, smoother than, and further than. And it's the word that follows other, rather, less, and more.
Then—the option to choose when time is involved—fits in the phrases just then and back then, and after words like since and until. It's also in the phrases and then some, every now and then, and even then.
In a handful of cases, though, than is used to say that something happens immediately after something else—that is, it's used when you're talking about something relating to time. So in "No sooner had I explained the rule than an exception came to mind," it's than not then that's required. And also in hardly had I explained it than and scarcely had I explained it than. (Sorry…)
So when did this pair get so confusing? Turns out they've always been that way. Linguistically speaking, they're identical twins. In Middle English, they were the same word; both spellings were used for all the various meanings. It's been a few hundred years, however, since English has treated them as distinct, which means we have to too. We could go back to Middle English, but we think that would be harder then—um, that is, harder than—mastering these.