We use those words to make questions and the negative. Questions: Do you speak English? Does your sister speak French? Did the train arrive on time? Negative: I DO not speak English. My sister DOES not speak French. The train DID not arrive on time. ***** Sometimes we also use it to emphasize something: Tom: I speak 10 languages. Mona: No, you don't. Tom: I am not lying. I DO speak 10 languages. And my sister speaks 15 languages. Mona: No way! Tom: Believe me! She DOES speak 15 languages!

Does (Simple Present Tense) Did (Simple Past Tense) We use "does" and "did" for questions and negative sentences, "does" is used only for 3rd person singular. For example: He plays basketball every day. - if you want to ask a question you say: Does he play basketball every day? When does the train leave? and negative sentences: He does not (doesn't) play basketball every day. She doesn't like dancing. Simple Past Tense is used for something that happened in the past. For example: He played basketball yesterday. When did he play basketball? He did not (didn't) play basketball yesterday. We didn't go to school last week.