How do you tell a spelling mistake from a grammar mistake? For example:

  1. Your the best.
  2. This iz the end.
  3. I likes music.
  4. She preatend to be asleep.

One method is to read the erroneous sentence aloud (let’s call it the ‘speech method’): if the sentence sounds correct then it has a spelling mistake, otherwise it has a grammar mistake. Applied to the examples, 1 and 2 have spelling mistakes, and 3 and 4 have grammar mistakes.

Another method is to look up each word of the erroneous sentence in a dictionary (let’s call it the ‘dictionary method’): if the sentence uses a word that is not in the dictionary, then it has a spelling mistake, otherwise it has a grammar mistake. Applied to the examples, 1 and 3 have grammar mistakes, and 2 and 4 have spelling mistakes.

The problem is that these two methods give different results (for 1 and 4, not for 2 and 3). Which method should I use?

  • 2
    You just have to know it. Sounds are not a good way to go. There are many words you may not know.....[You mean: if the sentence doesn't sound correct...]
    – Lambie
    Commented Apr 22, 2021 at 16:11
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    Does this answer your question? Spelling or grammar error? Commented Apr 22, 2021 at 18:20
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    If it's not written it can't be a spelling misteak. Commented Apr 22, 2021 at 23:32
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    @Maggyero - Hmm. Obviously you should use the method that gives the right answer. :-) Remember that just because a word is in the dictionary doesn’t mean it’s the write word four the sen tents.
    – Jim
    Commented Apr 23, 2021 at 8:40
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    @Maggyero What is the point of such a rule? Is it to answer questions on a test? Is it to improve an automated checker in an editor? Or is it proof reading a non-native speakers text to tell them how ti fix it? (the last two are similar). 'Your the best' could be spelling, could be grammar, but also could be a typo or spellcheck suggestion error. Your dictionary rule works as a first pass for -positive- spelling errors. You could then just say any ambiguous one like 'I likes music' is grammatical (even if it was a slip on the keyboard).
    – Mitch
    Commented Apr 23, 2021 at 13:08

4 Answers 4


You can’t always tell which type of mistake it is. It might be one or the other, or even both or neither. Consider the following:

  • This sentence has a spelling mistak.
  • This sentence are ungrammatical.
  • If the miss steaks are over there, perhaps it’s both.
  • if the missed steaks are over here, though, that might be intentional.

But to answer your question: you need to first try to understand the intent. Then if the sentence doesn’t match that intent, you can look more carefully for causes. Typos that result in words not recorded in dictionaries would be obvious spelling mistakes; but if all the words in the sentence are valid English words, things become a lot more messy.

If you consider grammatical correctness to be independent of intent (which is perfectly legitimate to do), it becomes a matching exercise to see if any combination of the tenets of your chosen grammar can produce the sentence.

The trap, however, is that there are numerous English dialects. It’s even worse with rhyming slang such as “He’s on the dog”: “dog and bone” rhymes with “telephone”, then you drop words out. It’s not a spelling mistake if it’s really what they wanted to say. Likewise, “Who ya callin’ short?” can be considered ungrammatical, but it’s completely idiomatic in some dialects.

In summary:

  • Spelling: pick a dictionary and try to find the words.
  • Grammar: pick a grammar and check if the sentence confirms to it.
  • General rule: check the text against the intent.
  • Comments are not for extended discussion; this conversation has been moved to chat.
    – tchrist
    Commented May 9, 2021 at 2:08

The distinction depends on what is on the mind of the person who is making the mistake: is that person mistaken about the relevant rules of English grammar, or merely about the spelling? When we see a mistake, we can usually think of a reasonable explanation of what led the person to make the mistake, and then classify the mistake accordingly. For example, it is reasonable to think that a person who wrote 'This iz the end' is relatively clear about how to structure this sentence and is only mistaken about the spelling of is. We would thus say that this is a spelling mistake.

Sometimes, it is, however, difficult to be sure what was on the person's mind. Did the person who wrote 'Your the best' want to write 'You're the best' and was mistaken in thinking that you're can be spelled as your? If so, this would be a spelling mistake. But maybe the person really wanted to write your and mistakenly thought that English syntax permits combining your and the best in this way. In that case, the person would be making a mistake about the grammar. Or, perhaps, the person knows that this combination does not fit the standard rules of the syntax, but mistakenly thinks that 'Your the best' is some sort of an idiom that is an exception to the standard rules. That would be a mistake of yet another kind. If we are not sure what was on the person's mind, we cannot be sure how to classify the mistake.

There is thus no simple rule for classification of such mistakes that can be applied solely on the basis of what the mistake looks like; the classification is always based on our (more or less reliable) reconstruction of how the person was led to make the mistake.

  • Thanks. But aren’t spelling mistakes restricted to words outside the dictionary (what I called the lexicon criterion in my post), making the spelling–grammar mistake distinction unambiguous? Extending spelling mistakes to words inside the dictionary does indeed require the author’s intent, so it would not be a useful definition.
    – Géry Ogam
    Commented Apr 22, 2021 at 20:53
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    I agree that from the writer’s perspective, ‘Your the best.’ can either be a spelling mistake (if he intended ‘You’re the best.’) or a grammar mistake (if he intended it). But from the reader’s perspective, since he does not now the writer’s intent, it seems to me that if he only looks at lexical correctness then the only possible conclusion is that it is a grammar mistake, and if he only looks at speech correctness then the only possible conclusion is that is it a spelling mistake. And my question was which of these two criteria (lexicon or speech) is used conventionally?
    – Géry Ogam
    Commented Apr 22, 2021 at 22:08
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    @Maggyero - It is reasonable to assume that "Your the best" is intended to mean "You're the best" because that is a common expression that makes sense, whereas other attempts to give meaning to it based on "your" rather than "you're" don't really make sense. Also it is likely that there would be context thatI further reinforces that meaning. It's a spelling mistake.
    – nnnnnn
    Commented Apr 23, 2021 at 8:51
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    @nnnnnn In other words, you think that the ‘speech method’ in my post should be used?
    – Géry Ogam
    Commented Apr 23, 2021 at 8:55
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    @Maggyero, if the reader does not know the writer's intent, then the reader does not know what kind of a mistake has been committed. In most cases, however, the reader can fairly easily discern the intent. The reader does so on the basis of the totality of the circumstances in which the mistake has occurred, not by mechanically applying some method to which one has committed oneself in advance.
    – jsw29
    Commented Apr 23, 2021 at 16:01

Grammar is in the ear; spelling, the eye.

spoken/sounds wrong written/looks wrong error in
no no none
yes no grammar
no yes spelling
yes yes both

If it sounds right when you hear it spoken but not when you see it written, then it cannot be a grammatical error. It can only be an error in orthographic transcription.

Grammar faults cannot be seen, only heard, because grammar is a property peculiar to the real language, the spoken one.

Spelling faults cannot be heard, only seen, because spelling is a property peculiar to the technology of writing. The same is true of such things as upper- versus lowercase, compound words with or without any separators, italic versus roman, kerning and ligatures, and much else besides. Technology is complicated.

Like all other technology, spelling is an invention, a deliberate creation, not the natural product of the human brain’s neurological hardware. It is constantly being fiddled with by its technologists, and fumbled with by those less well taken to such technologies.

Grammar was not created by deliberate intent over the ages. It developed organically, even unconsciously, in the minds of its living speakers. It continues to do so just as long as that language remains spoken, and then it does not. Once an organism dies, organic growth ceases. So too with language.

  • I think you have the 1st two column labels switched.
    – Mitch
    Commented Apr 23, 2021 at 18:47
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    Is this question more prototypical than the original? No research is mentioned here; it could be speculation. Commented Apr 23, 2021 at 18:59
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    ‘grammar is a property peculiar to the real language, the spoken one.’ I agree for oral languages. But for written languages like the Python programming language, the grammar is not in the ear but in the eye. In this case can we still talk about a grammar mistake vs a spelling mistake (or more generally a grammar mistake vs an orthography mistake, since orthography includes spelling, hyphenation, capitalization, word breaks, emphasis, and punctuation)?
    – Géry Ogam
    Commented Apr 23, 2021 at 21:58
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    It seems that look and see are used here in some metaphorical senses, which need to be explained. In the ordinary, literal senses of these words grammatical mistakes do look wrong, and one does see that they are wrong. Most people don't need to vocalize a sentence with a grammatical mistake to realise that it embodies a mistake.
    – jsw29
    Commented Apr 24, 2021 at 16:05
  • @jsw29 Yes, when I said ‘read aloud’ and tchrist said ‘hear’, we did not mean literally. We mean speaking in our head. It is to abstract the sentence away from its written representation.
    – Géry Ogam
    Commented Apr 26, 2021 at 8:50

In communication, an origin/source/sender/encoder (who) encodes a message/content (what) into a signal/form (how) and sends it to a channel/path/line/medium. A destination/sink/receiver/decoder (to whom) receives a corresponding signal/form (how) from the channel/path/line/medium and decodes it into a message/content (what).

To properly answer the question, one should distinguish between encoding errors, signal defects, decoding failures, decoding errors and message defects (the terms ‘error’, ‘defect’ and ‘failure’ are borrowed from software testing). An error in a process (encoding or decoding) may result in a defect in its product (encoded signal or decoded message), and a defect in a product (encoded signal) may result in a failure in a subsequent process (decoding).

An encoding error at the lexical level or grammatical level may result in

  • a signal defect at the lexical level (e.g. ‘This iz the end.’), in which case the destination can detect the encoding error, can classify the encoding error as lexical and can correct the signal defect to the nearest valid signal (e.g. ‘This is the end.’); or
  • a signal defect at the grammatical level (e.g. ‘Your the best.’), in which case the destination can detect the encoding error, cannot classify the encoding error and can correct the signal defect to the nearest valid signal (e.g. ‘You’re the best.’, which happens to be a heterograph of the defective signal); or
  • no signal defect (e.g. ‘Give me an egg sample.’), in which case the destination cannot detect the encoding error, cannot classify the encoding error and cannot correct the signal defect.

Thus, unless the destination knows the origin’s message, the destination can only detect lexical encoding errors resulting in lexical signal defects. However the destination can always detect lexical and grammatical signal defects.

Coming back to the examples given in the question: ‘Your the best.’ and ‘I likes music.’ have an encoding error (of unknown level) resulting in a grammatical signal defect, while ‘She preatend to be asleep.’ and ‘This iz the end.’ have a lexical encoding error resulting in a lexical signal defect.

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