是 (shì) means “to be (followed by substantives only); correct; right; true; (respectful acknowledgement of a command) very well; (adverb for emphatic assertion)”. It is an HSK 1 Chinese character in the HSK 3.0 vocabulary.
他是我的老师。
Tā shì wǒ de lǎoshī.
He is my teacher.
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