Homophones and real-word errors: the mistakes spell checkers miss
A dictionary-based spell checker asks one question: is this a word? Their, there and they're all are, so it waves every one of them through, whichever you meant.
Why checkers miss them
Researchers call these real-word errors: a slip that happens to produce another valid word. Karen Kukich's widely cited survey, "Techniques for automatically correcting words in text" (ACM Computing Surveys, 1992), separates them from non-word errors precisely because they need a different kind of solution. A non-word like recieve can be caught by lookup. A real-word error can only be caught by understanding context: which word fits this sentence. That requires grammar rules or a statistical or neural language model, which is what grammar checkers and some modern word processors add on top of plain spell checking.
Homophones (words that sound alike) are the most common source, but not the only one. Typing slips such as form for from, out for our or manger for manager, and dropped letters such as of for off, are just as invisible. The Letterbench spell checker is a lookup checker, so everything on this page is on you.
The pairs that matter most
its / it's
It's always means it is or it has. Its is the possessive: the cat licked its paw. Test: replace it with it is. If the sentence still works, you need the apostrophe. The confusion comes from the fact that most English possessives do use an apostrophe (the cat's paw); possessive pronouns (his, hers, ours, its) never do.
their / there / they're
They're = they are. Their = belonging to them. There = a place, or the dummy subject in there is. Aids: there contains here, both places; their contains heir, someone who owns things.
your / you're
You're = you are; your = belonging to you. The same expansion test works.
affect / effect
In most everyday writing, affect is the verb (the weather affects my mood) and effect is the noun (the weather has an effect on my mood). An aid: action, affect; end result, effect. The exceptions are real but rarer: effect as a verb means "to bring about" (to effect change), and affect as a noun is a term in psychology for displayed emotion.
then / than
Than compares (taller than me); then is about time or consequence (first this, then that; if so, then...).
lose / loose
Lose (one o) is the verb: to lose your keys. Loose is the adjective: a loose screw. Loose has lots of room, so it gets two o's.
principal / principle
A principle is a rule or belief; both end in -le. Principal means main, or the head of a school, or the capital sum of a loan.
complement / compliment
A complement completes something (the wine complemented the meal); a compliment is praise. Complement and complete share the e.
stationary / stationery
Stationary means not moving; stationery is paper and envelopes. E for envelope, and for pen.
discreet / discrete
Discreet means tactful; discrete means separate, distinct. In discrete, the t separates the two e's, which is what the word means.
who's / whose
Who's = who is or who has. Whose is the possessive. Same expansion test as it's.
Other pairs worth a second look
| Pair | Quick distinction |
|---|---|
| accept / except | accept = receive; except = excluding |
| advice / advise | noun with c, verb with s (in both British and American usage) |
| breath / breathe | noun / verb: take a breath, breathe in |
| capital / capitol | capitol is the building where a legislature meets (in the US); capital for cities, money, letters |
| cite / site / sight | cite a source; a building site or website; the sense of sight |
| ensure / insure | insure is mainly about insurance policies; ensure = make certain (usage varies between US and UK) |
| peak / peek / pique | mountain top; quick look; to arouse (interest) |
| rein / reign / rain | free rein (from horse riding); a monarch's reign |
| to / too / two | too = also, or excessively |
| weather / whether | whether introduces alternatives |
When usage is genuinely disputed, a dictionary usage note is the authority to consult; Merriam-Webster and the Oxford English Dictionary both publish them.
Proofreading for real-word errors
Because no lookup will help, these errors need a deliberate pass of their own. A few methods that work:
- Search for the usual suspects. Use your editor's find function for its, it's, their, there, your, then, affect, effect and lose. Checking twenty highlighted words takes a minute and catches most problems.
- Expand contractions in your head. Every it's, you're, they're and who's should survive being read as it is, you are, they are, who is.
- Read aloud, slowly. Typing slips such as form/from jump out when spoken, because the sentence suddenly makes no sense.
- Change the view. Print the text, switch font or read it on your phone. Familiar layout encourages the eye to see what it expects.
- Use a grammar checker as a second opinion, not a replacement: context-aware tools catch many confusions, but they also miss some and occasionally suggest a wrong "fix".
Why it matters
A typo like teh reads as a slip of the finger. A wrong homophone reads, fairly or not, as not knowing the difference, and readers notice: your welcome and loose weight are the kind of errors that become screenshots. The good news is that the list of pairs that cause most of the trouble is short. Learn the dozen above, and add a search for them to your final proofreading routine alongside a normal spell check. For the non-word side of the problem, see commonly misspelled words.