Rules for Adding 's' to Verbs in Third (3rd) Person Singular

In the present simple tense, we add 's' (or sometimes 'es') to the base form of the verb only for he, she, or it (third person singular). 

Here are the rules:

For most verbs, just add 's':

• I play → He plays
• I sing → She sings
• I run → It runs

For verbs ending in -s, -sh, -ch, -x, or -o, add 'es':

• I pass → He passes
• I wash → She washes
• I watch → It watches
• I fix → He fixes
• I go → She goes

For verbs ending in consonant + y, change 'y' to 'i' and add 'es':

• I try → He tries
• I cry → She cries
• I fly → It flies

For verbs ending in vowel + y, just add 's':

• I play → He plays
• I say → She says

Some irregular verbs:

• I have → He has
• I do → She does /dʌz/