Rule 7

‘dis’ and ‘mis’

Never double the ‘s’ of these prefixes. When a second ‘s’ occurs, it is the first letter of the next syllable.

So we have

Dismiss (NOT Dissmiss)
Misplace (NOT Missplace)

BUT

Dissent (Here the second ‘s’ is the first letter of the next syllable ‘sent’.)
Misspell (Here the second ‘s’ is the first letter of the next syllable ‘spell’.)

Rule 8

When followed by ‘ing’

When followed by ‘ing’, the ‘e’ is always dropped, except when the final ‘e’ is preceded by a vowel with which it forms one sound. Examples are given below:

See, seeing
Dye, dyeing

Rule 9

Words ending in ‘c’

Words ending in ‘c’ take ‘k’ after the ‘c’ before adding ‘ed’ or ‘ing’.

Examples are:

Frolic, frolicked
Mimic, mimicked

Nouns ending in ‘y’ preceded by a consonant form the plural by changing ‘y’ into ‘ies’.

Army, armies
Lady, ladies

Note that if ‘y’ is preceded by a vowel, only ‘s’ is added.

Monkey, monkeys
Boy, boys
Toy, toys

Rule 10

Nouns ending in ‘ch’, ‘s’, ‘ss’, ‘sh’, ‘x’ and ‘z’ form the plural by adding ‘es’.

Church, churches
Fox, foxes
Brush, brushes
Glass, glasses

Most nouns ending in ‘o’ form the plural by adding ‘es’.

Tomato, tomatoes
Potato, potatoes
Hero, heroes

Note that there are several exceptions to this rule.

Examples are: photo, photos; piano, pianos; buffalo, buffalos

Rule 11

Nouns ending in ‘f’ or ‘fe’ form the plural by changing the ‘f’ or ‘fe’ into ‘v’ and adding ‘es’.

Knife, knives
Leaf, leaves
Half, halves
Loaf, loaves
Shelf, shelves
Wife, wives

Exceptions

There are several exceptions to this rule:

Chief, chiefs
Dwarf, dwarfs
Roof, roofs
Hoof, hoofs
Proof, proofs

Rule 12

In case of words ending in ‘cede’ or ‘ceed’ or ‘sede’, ‘cede’ is to be used in all words except the following four words: proceed, exceed, succeed and supersede.