Verb is added with -s/-es if the subject is 3rd person singular personal pronoun.
e.g. A bird sings outside my windows.
It sings loudly
Ann sings beautifully
She sings songs to her children
Tom sings very well
He sings in a chorus

(Examples are taken from Fundamentals of English Grammar)



Most verbs are added with final -s
visit >>> visits
speak >>> speaks
ride >>> rides
write >>> writes

Words end in -ch, -sh, -s, -x, and -z are added with final -es
catch >>> catches
wash >>> washes
miss >>> misses
fix >>> fixes
buzz >>> buzzes

If a word ends in a consonant + -y, change the -y to -i and add -es.
fly >>> flies

If a word ends in a vowel + -y, simply add -s
pay >>> pays

The singular forms of the verbs go, do, and have are irregular
go >>> goes
do >>> does
have >>> has