How do you tell a spelling mistake from a grammar mistake?

Question

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?

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.