This page explains what inflections are and gives examples of the rules governing them.

Inflection is the name for the extra letter or letters added to nouns, verbs and adjectives in their different grammatical forms. Nouns are inflected in the plural, verbs are inflected in the various tenses, and adjectives are inflected in the comparative/superlative.

Here are some of the most important inflection rules:

Word form
1. Words ending with a sibilant: -s/-ss/-sh/-ch/x.
2. Words ending with the letter -o.
Inflection rule
Add -es in the plural noun or 3rd person singular verb.
bus → buses (n) / busses (v)
miss → misses
wish → wishes
watch → watches
fox → foxes
potato → potatoes
do → does

Word form
Words ending consonant -y.
Inflection rule 1
Change the -y to ie before the ending -s.
party → parties
study → studies
cry → cries
Inflection rule 2
Change the -y to i before the endings -ed /-er /-est.
try → tried
happy → happier
easy → easiest
Inflection rule 3
Do NOT change the -y before the ending -ing.
carry → carrying
try → trying

Word form
Words ending vowel -y.
Inflection rule
Do NOT change the -y.
buy → buys
play → played

Word form
Words ending with the letters -ie.
Inflection rule
Change the -ie to a -y before the ending -ing.
die → dying
lie → lying

Word form
Verbs ending consonant -e.
Inflection rule
Omit the -e before the ending -ing.
ride → riding
love → loving
write → writing
provide → providing

Word form
1. One-syllable words ending consonant-vowel-consonant.
2. Two or more syllable words ending consonant-vowel-consonant that are stressed on the last syllable.
Inflection rule
Double the last consonant before the endings -ing /-ed /-er /-est.
hit → hitting
stop → stopped
wet → wetter
fat → fattest
begin → beginning
prefer → preferred

Word form
Two or more syllable words ending consonant-vowel-consonant that are stressed on the first syllable.
Inflection rule
Do NOT double the last consonant before the endings -ing /-ed /-er /-est.
happen → happening
visit → visited

Note: There may be some exceptions to the inflection rules above, especially for new words. For example: the -ing form of the verb to skype is spelled as skypeing by some people. And you will see both typos and typoes.

So to be absolutely sure of any given inflection, it is best to consult a good dictionary or to rely on your computer spell-checker to guide you.

Do a quiz on this grammar topic.