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?

  • The dictionary method is obviously not going to be reliable – anything erroneously written, whether borne out of grammar or only orthography, can by coincidence end up matching an existing word. Simply checking to see whether a word is in a dictionary with no reference to context is virtually pointless. (Incidentally, 3 would likely also be considered a spelling error under this method, since inflected forms like likes are not generally listed in dictionaries.) Apr 23, 2021 at 10:03
  • Is there any particular purpose for which you desire a particular method? Depending on your purpose one might be more useful than another.
    – 007
    Apr 23, 2021 at 13:39
  • @user916972 The purpose is to proofread documents for spelling and grammar mistakes. The causes of the mistakes (typing error, lack of knowledge, lack of concern, etc.) are of course unknown.
    – Géry Ogam
    Apr 23, 2021 at 13:58
  • 5
    Your question has already been answered on ELU. This question is exactly the same as that on ELU. Apr 23, 2021 at 21:45

1 Answer 1


Insofar as the purpose of identifying mistakes is proofreading, the classification of mistakes is less important than the identification thereof.

The difference between a spelling and a grammar mistake may depend on context, especially when dealing with verb forms. Omitting an s from the third person singular of the simple present tense could be construed as either incorrect spelling or grammar.

In the end, there is no substitute for knowledge of the language. Especially if you're proofreading something written in casual language, a departure from standard grammar and spelling is to be almost expected. In such a case, without being acquainted with the particular register or dialect concerned, correct identification of mistakes may not be possible.

  • there is no way to construe lack of third person -s as a spelling mistake.
    – vectory
    Sep 22, 2021 at 10:53

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