How is 'does' correctly used in sentences?

The word 'does' is the third-person singular present-tense form of the verb 'do' and is used in specific grammatical contexts. It pairs exclusively with third-person singular subjects, including pronouns like 'he,' 'she,' and 'it,' demonstratives like 'this' and 'that,' and singular nouns such as 'the dog' or 'my teacher.'

Key Uses of 'Does'

1. ·Forming Yes/No Questions: 'Does' typically starts the question, followed by the subject and the base form of the main verb (which loses its final 's' from the affirmative sentence). Example: 'Does she speak Spanish?' (from the affirmative 'She speaks Spanish.')
2. ·Forming Wh-Questions: 'Does' comes after wh-words (who, what, where, etc.). Example: 'What does he need for the project?'
3. ·Negations: 'Does' is used in its contracted form 'doesn’t' to deny actions for third-person singular subjects. Example: 'Your client doesn’t understand the contract.'
4. ·Adding Emphasis: 'Does' can reinforce the main verb in affirmative sentences, often to clarify or counter doubt. Example: 'She does finish her homework every night.'

Important Restrictions

• ·'Does' is never used in imperative sentences (commands).
• ·It is not added to sentences that already include a modal verb (can, must), a 'to be' verb (am, is, are), or another helping verb (have). For example, 'He does can swim' is incorrect; the correct form is 'He can swim.'
• ·'Does' is rarely the first word in non-yes/no questions.