SPELLING of the verb in the 3rd person singular "Vs"
1.Exception: "be"isbe - is
 Exception: "have"hashave - has
 Exception: modal verbs 
we don't add "s"
can - can
may - may
must - must
should - should
If the verb ends in
 - ss
 - sh
 - ch
 - x
 - o
 - z
we add "es"
dress - dresses
wash - washes
teach - teaches
box - boxes
go - goes
waltz - waltzes
If the verb ends in
consonant* + y
we change "y" to "ie
and add "s
tidy - tidies
fly - flies
If the verb ends in
vowel* + y
we just add "s
play - plays
buy - buys
5.In other caseswe just add "swork - works
*Vowels: a, e, i, o, u
*Consonants: b, c, d, … x, y, z (all the other letters)
Vs — Present Simple verb (for he, she, it). E.g. writes, goes, listens, etc.