5. Adding Endings

There are two kinds of suffixes, those that begin with a vowel and those that begin with a consonant. As usual, the spelling problems occur with the vowels: 

Vowel Suffixes

Consonant Suffixes

- - - age - - -ist - - - ness - - - cess
- - - ant - - - ish  - - -less - - -ment
- - -ance - - -ing - - -ly - - -ty
- - - al - - -ar - - -ful - - -ry
- - -ism - - -o - - -hood - - -ward
- - -able - - -on - - -wise  
- - -an - - -ous    
- - - a - - -or    
- - -es - - -ual    
- - -ed - - -unt    
- - -er - - -um    
- - -est - - -us    
- - -y - - -ive    

1. Words that end in the letter y must have the y changed to i before adding any suffix:

body - bodily  marry - marriage
many - manifold family -  familiar
happy - happiness puppy - puppies
beauty - beautiful vary - various
company - companion fury - furious
plenty - plentiful merry - merriment

2. In words that end in a silent e you must drop it before you add a vowel suffix. The silent e is no longer needed to make the preceding vowel long as the incoming vowel will do the trick:

ride - riding cure - curable use - usual age - aging
fame - famous force - forcing refuse -  refusal slice - slicing
pure - purity ice - icicle nose - nosy convince - convincing
globe - global race - racist pole - polar offense - offensive

3. Words that end in an accented short or modified vowel sound must have the final consonant doubled to protect that sound when you add a vowel suffix:

Quebec - Quebecker remit - remittance confer - conferring refer - referred
upset - upsetting shellac - shellacking occur - occurred concur- concurrent

Note that this doubling is not done if the accent is not on the last syllable. If the word ends in a schwa, there is no need to "protect" it.

open - opening organ - organize
focus - focused refer - referee

4. Normally you drop a silent e before adding a vowel suffix. However, if the word ends in -ce or -ge and the incoming vowel is an a, o, or u, you cannot cavalierly toss out that silent e. It is not useless: it is keeping its left-hand letter soft, and your a, o, or u will not do that. Thus:

manage - manageable peace - peaceable
courage - courageous revenge - vengeance
surge - surgeon change - changeable
notice - noticeable outrage - outrageous

Gorgeous George bludgeoned a pigeon noticeably! Tsk.

5. Adding consonant suffixes is easy. You just add them. (Of course you must change a final y to i before you add any suffix.)

peace - peaceful harm - harmless age - ageless
pity - pitiful child - childhood rifle - riflery

5.2. /sh/

When this sound occurs before a vowel suffix, it is spelled ti, si, or ci.

partial cautious patient vacation
special deficient suspicion suction
inertia delicious ratio pension
musician physician optician quotient
electrician nutrition statistician expulsion

5.3. /ee/ before a vowel suffix

When /ee/ precedes a vowel suffix, it is usually spelled with the letter i:

Indian obvious medium
ingredient zodiac material