Use than for comparisons and then for time, sequence, or a conclusion. “The walk was longer than I expected” compares the walk with an expectation; “We ate, then walked” orders two events. The words sound alike in many varieties of English, but their jobs in a sentence differ. Purdue OWL makes this same basic distinction, describing than in comparisons and then in time, order, and logical conclusions. [1]
Than sets two things side by side
Than introduces the other side of a comparison: taller than the fence, quieter than yesterday, more curious than cautious. It can compare actions too: “I would rather listen than interrupt.” In each case, the sentence asks the reader to measure one person, quality, amount, or choice against another.
Try replacing than with “compared with.” “This route is shorter than the old one” becomes “This route is shorter compared with the old one.” The wording is a little less natural, but the relationship remains. If the substitution makes sense, than is likely right. A comparison can be explicit or elliptical: “She reads more than I do” leaves the second amount understood, but than still introduces the comparison.
Then moves through time or logic
Then can mean “at that time”: “I lived near the harbor then.” It can also mean “next” in a sequence: “Fold the paper, then turn it over.” A third common use marks a conclusion: “If the room is already booked, then we need another venue.” The word links the condition to what follows; it does not compare the room with anything.
A useful substitution is “next” for sequence or “in that case” for a conclusion. “Check the address, then send the parcel” means check first and send next. “If the address is wrong, then the parcel may go astray” means in that case. When neither substitute works but “compared with” does, choose than.
Read a short scene for both
Consider this original pair: “The bus arrived later than the timetable suggested. We waited under the awning, then crossed the square together.” The first sentence compares the arrival time with the timetable’s prediction. The second puts waiting before crossing. Replace then with than and the sequence disappears; replace than with then and the comparison no longer works.
Now try a more subtle example: “If the gallery closes early, then we’ll sketch outside; the garden is quieter than the cafe.” Then signals the result of a condition. Than compares two places by noise level. In a paragraph containing both words, their different functions can be easier to notice than when proofreading isolated words.
Check for the common keyboard slip
Because the words are pronounced alike for many speakers, typing by sound can produce a wrong choice even when the intended meaning is clear. Run a search for every then and than in a draft. For each than, point to the two things being compared. For each then, name the time, next step, or conclusion it signals. If you cannot identify the relationship, reread the clause around it.
This check also catches sentences where the word is technically correct but the comparison is incomplete or unclear. “The new version is better than before” may be understood, but “better than the earlier version” names the comparison more precisely. Purdue’s guidance on sentence clarity recommends making relationships between old and new information easy for readers to follow; naming the compared item can do that work. [2]
A compact editing exercise
Take these invented lines: “Mina was more patient then her partner. She listened, than wrote a reply.” First ask whether the sentence compares two people: it does, so write “more patient than her partner.” In the next line, listening comes before writing, so write “listened, then wrote a reply.” The comma is a separate punctuation choice; the key decision comes from the meaning relation.
Make your own two-line example with one comparison and one sequence. Put a pencil mark under the words being compared, then number actions in the order they happen. This simple visual check keeps the spelling tied to the thought: comparison calls for than; time and consequence call for then.
