Remember suffixes are small words that we add to the end of words to make new words or change the grammar.

Sometimes we have to change the root word and sometimes double up letters so let's have a look at some rules around adding suffixes.

Watch the video and/ or read below.

For more lessons and videos on spelling rules click on the ones below
Drop the 'e' rule
Only use full when full
1:1:1 doubling up rule

First we need to understand what vowel and consonant suffixes
are for this part
vowel suffix
-ance
-er
-ing
-able/-ible
-est
-ed
-ation


consonant suffix
-ly
-less
-y
-ship
-ment
-ness
-ful
-s 

Summary of some key rules ( but like all spelling rules there are always exceptions)

1.  Y to i rule with words ending in consonant + y.

a. Change the y to i before vowel suffixes (except -ing) 

carry + ed =  carried 
carry + er = carrier
carry + age = carriage
BUT carry + ing = carrying (can't have two i's carriing!!!!! But exceptions see rule 5)

happy + er = happier
happy + est = happiest

supply + ed = supplied
supply + er = supplier
supply + es = supplies
BUT supplying

deny - denied, denial BUT denying
marry - married, marries BUT marrying
rely - reliable, reliant, relied, relies BUT relying
comply - compliance, compliant, complied, complies, BUT complying

b. Change the y to i before consonant suffixes

beauty + ful = beautiful
beauty + fy = beautify

happy + ness = happiness
happy + ly = happily

angry - angrily, angriness
ordinary - ordinariness, ordinarily
lonely - loneliness
empty - emptiness
plenty - plentiful
likely- likeliness, likelihood
necessary = necessarily
busy - business, busily
hungry - hungrily

c. exceptions - dryer, drying, dryish, dryness, slyness

dry + ly = dryly or drily

d. Changing ie to y

die + ing = dying
tie + ing = tying
lie + ing = lying

e. y remains if the word ends in a vowel + y

buy - buyer, buying, buys
employ - employer, employee, employable
enjoy - enjoying, enjoyed, enjoyable, enjoyment
joy - joyful, joyous, enjoyable, joys

2. Drop the 'e' rule before a vowel suffix

a. Words ending in silent 'e'  + vowel suffix

love - loving, lover, loved, lovable (or loveable)
make - making, maker
use - using, usable, user, used
have - having
adore- adorable
care - cared, carer, caring
move - movable, moving, mover

b. Exceptions - words ending in 'ce' or 'ge' keep the 'e' before -ous and -able ( because it softens the 'g', 'c' sound)

manage - manageable  (BUT  drop the 'e' with -ing, -ed, er  managing, managed, manager)

notice - noticeable  (BUT drop the 'e' with -ing etc noticing, noticed)

courage - courageous
service - serviceable
changeable
gorgeous

c. Also keep the 'e' with the following:

likeable, saleable, hireable, blameable, sizeable nameable ( but drop the 'e' with -ing)

d. Also drop the 'e' with -is
analyse + is = analysis,  paralyse = paralysis

Keep the 'e' rules:

e. Keep the 'e' with consonant  suffixes

Keep the 'e' before -ful

care+ ful = careful
hopeful, peaceful, useful, wasteful

BUT change words ending in consonant + Y to i

plenty + ful = plentiful, beauty + ful - beautiful

BUT not joyful  = vowel + y

f. Keep the 'e' when the word ends in ee or ye 

agree - agreeing
eye- eyeing
see - seeing
guaranteeing, foreseeing, decreeing

g. Keep the 'e' before -ly

accurate+ ly = accurately, like + ly = likely, love+ ly = lovely, definite + ly = definitely

lively, rarely, homely, desperately, approximately, entirely, completely

BUT due - duly, subtle = subtly, true - truly

g. Keep the 'e' before -ment  

achieve + ment = achievement, advertisement, arrangement, excitement, involvement, replacement

BUT drop the 'e' with argue + ment = argument.

Also acknowledgement or acknowledgment can be spelt either way.

judgement usually keeps the 'e' but lawyers spell it without the 'e' judgment

3. 1:1:1 rule - Check out the 1:1:1 doubling up video

a. Words of 1 syllable ending in 1 vowel+ 1 consonant - double the last letter before a vowel suffix

shop - shopped, shopping, shopper
plan - planned, planning, planner
fat - fatter, fatten, fattest, fatty
pot - potting, potted, potter, pottery
slip - slipped, slipping, slipper, slippery

Do not double last letter if it's a w, x, y - tax - taxed, stay - staying, towed...
Do not double if two vowels - heat - heating, sleeping, sleeper...
Do not double if two consonants - sharp- sharpen, fasting, turned...

BUT qu- is classed as one consonant because we can't have q without the u
quit - quitting, quitter, quitted
quiz - quizzed, quizzing, quizzer

b. Words of more than 1 syllable ending in 1 vowel + 1 consonant when the stress is on the last syllable double up the last letter.

regret - regrettable, regretting, regretted
forget - forgettable, forgetting (past: forgot - forgotten)
occur - occurring, occurrence, occurred
begin - beginning, beginner
commit - committing, committee, committed
forbid - forbidden, forbidding

BUT

prefer - preferring, preferred (BUT preference, preferable, preferential- the stress moves)
refer - referred, referring (BUT reference, referee- the stress moves)
confer - conferred, conferring (BUT conference)

(No change if stress not on last syllable - (stress on first syllable) target - targeted, limit - limited, limiting, budgeting, marketing, marketed)

BUT focus can be both - focusing or focussing, focused or focussed

ALSO  input - inputted, inputting
kidnap - kidnapped, kidnapping, kidnapper (American English can also have kidnaped, kidnaping, kidnaper but these are less common now.)
output - outputted, outputting
worship - worshipping, worshipper, worshipped ( American English can also have worshiped, worshiper, worshiped but these are less common now.)
handicap - handicapped, handicapping, handicapper

4. Double the last L
Words of more than 1 syllable ending in 1 vowel + L always double up the L before a vowel suffix (except after -ity and -ise). American spelling don't double up. 

travel - travelled, traveller, travelling) (American - traveled, traveler, traveling)
cancel - cancelling, cancelled, cancellation (American - canceling, canceled, cancelation)
label - labelling, labelled (American - labeled, labeling)
model - modelled, modelling, modeller (American - modeled, modeling, modeler)
marvel - marvellous, marvelled, marvelling (American - marvelous, marveling, marveled)
signal - signalling, signalled, signaller signally (American - signaled, signaler, signaling)
quarrel - quarrelling, quarrelled, quarreller (American - quarreling, quarreled, quarreler)

enrol - enrolling, enrolled (enrols) (American enroll - enrolling, enrolled, enrolls)

expel - expelled, expelling, expeller, expellable (American the same)

BUT: devil - devilish, loyal - loyalist, parallel - paralleled, paralleling, travel - travelogue

Do not double when two vowels - appeal - appealing, appealed

5. Words ending in vowels   - no change with vowel suffixes.

echo - echoed, echoer, echoing
henna - hennaed
mascara - mascaraed
radio - radioed
ski - skied, skier, skiing
taxi - taxied, taxiing
video - videoed, videoing
These words are from other languages or new words like video, radio.

Spelling Rules Workbook
a step-by-step guide to the rules of English spelling
(suitable for British and American users)

200 pages of spelling rules and exercises.