As Chinese is a tone language you can not emphasize certain words or parts of a sentence by stressing them with a falling tone. Therefore, Chinese use the word 是 shì in order to emphazise certain parts of a sentence.
Emphasis on Subject
| 是 | 我 | 学 | 汉 | 语 | 。 |
| shì | wǒ | xué | hàn | yǔ | _ |
| be | I | study | Chinese ethnicity | language | _ |
| to be, correct, yes | I, me, my | study, learn | Chinese language | 。 | |
| I study Chinese. | |||||
Emphasis on Adjective
| 中 | 国 | 是 | 很 | 大 | 。 |
| zhōng | guó | shì | hěn | dà | _ |
| middle | country | be | very | big | _ |
| China | to be, correct, yes | very, quite | big, old, main | 。 | |
| China is really very big. | |||||
Emphasis on Action
| 他 | 是 | 学 | 汉 | 语 | 。 |
| tā | shì | xué | hàn | yǔ | _ |
| he | be | study | Chinese ethnicity | language | _ |
| he, him, other | to be, correct, yes | study, learn | Chinese language | 。 | |
| He actually studies Chinese. | |||||