He likes pears. (negative sentence) ¡æ

He is the third person singular, so you should put doesn't before the base form of the verb like. Then you can change the affirmative sentence into the negative sentence as follws.
He doesn't like pears. Remember that you should use the base verb 'like' after 'don't' or 'doesn't'.

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Is my explanation above grammatical? Are there any wrong uses of articles? I'd like you to check the expressions above.

He is the third person singular, so you should put doesn't before the base form of the verb like. Then you can change the affirmative sentence into the negative sentence as follows:

He doesn't like pears.
Remember that you should use the base verb like after don't or doesn't.

I corrected spelling and punctuation in bold.

When you are referring to a word or phrase or sentence as a word, not a grammatical part of the sentence, you should use italics (or underlining if you're writing by hand):
http://grammar.ccc.commnet.edu/grammar/italics.htm

Your use of articles is fine.

=)

Your explanation is almost perfect! Here are a few minor corrections:

1. Instead of using the symbol ¡æ, you should use the word "Doesn't" to negate the sentence. So the negative sentence would be: "He doesn't like pears."

2. When you said, "He is the third person singular," you were explaining the grammar rule correctly, but it would be clearer to say, "Since 'he' is the third person singular pronoun..."

Regarding your question about articles, you did not use any articles in your explanation, so there are no errors in the use of articles.

Overall, your explanation is clear and accurate with only a couple of minor corrections. Well done!