The basic spelling rules presented in the previous section are applicable to the spelling of thousands of words.  However, commonly used words that are exceptions to these rules are the concern of this section.

RULE: When a word ends in a single consonant preceded by a single vowel and the word is one syllable or accented on the last syllable, then double the final consonant when adding a vowel suffix.

beg begged begging
occur occurred occurring

Exceptions: Words ending in -w or -x

flow flowed flowing
fix fixed fixing

(Also remember that it is transferred and transferring)

RULE: When adding a vowel suffix to a word ending in -e the -e is dropped.

care + ed + ing cared caring  
desire + ed + ing desired desiring desirable

Exceptions: To prevent confusion with other words or for pronunciation purposes, the following words are exceptions:

acre acreage
canoe canoeing
dye dyeing (to change color)
mile mileage
singe singeing (to burn slightly)

(Also remember that for words ending in -ce or -ge, the -e is kept if the vowel suffix begins with -a or -o.)

RULE: Adding a consonant suffix does not change the spelling of a word.

pain + ful painful
rapid + ly rapidly
complete + ly completely

Exceptions:

acknowledge + ment acknowledgement
argue + ment argument
judge + ment judgment
nine + th ninth
true + ly truly

RULE: If a word ends in -y preceded by a consonant, change the y to -i, then add the suffix.

beauty + ful beautiful
try + ed tried

Exceptions:

dry + ness dryness
shy + ness shyness
sly + ness slyness

(Also remember that the y is kept then adding -ing.)

RULE: If a word ends in y preceded by a vowel, then the y is kept when a suffix is added.

annoy + ed + ing annoyed annoying
journey + ed + ing journeyed journeying

Exceptions:

day + ly daily

RULE: A prefix does not change the spelling of a word

dis + able disable
un + necessary unnecessary

Exceptions: none

RULE: When two words are joined to form a compound word, omit no letters.

room + mate roommate
book + keeper bookkeeper

Exceptions:

past + time pastime
where + ever wherever

 

Reference:
- Holt, Rinehart and Winston, Inc., 1989