SIMPLE RULES OF ORTHOGRAPHY
1. Monosyllablic words which end in f, l, or s, when preceded by a single vowel, double their final letter: e.g., muff, still, lass. Exceptions: clef, of, if, bul, nul, sal, sol, as, gas, has, was, yes, gris, is, his, this, pus, us, thus.
2. Monosyllabic words which end in consonants other than f, l, or s do not double their final letter. Exceptions: abb, add, ebb, odd, mumm, inn, bunn, err, purr, burr, butt, mitt, fizz, fuzz, buzz.
3. Monosyllabic words ending in a consonant immediately following a diphthong or a double vowel do not double their final letter. Exception: guess.
4. In monosyllables and words accented on the final syllable ending with a single consonant (excepting h or x) preceded by a single vowel, or by qu and a vowel, the final consonant is doubled before an added {34} termination beginning with a vowel, irrespective of the addition of another syllable: e.g., stop, stopped; regret, regretting. When, however, the place of the accent is changed by the added termination, the final consonant is not doubled: e.g., prefer´, pref´erable.
5. In monosyllables and words not accented on the last syllable, an added termination does not double the final consonant when it is preceded by a diphthong or by two vowels: e.g., profit, profited; cancel, canceled; benefit, benefited; equal, equality, novel, novelist, and all the derivatives of parallel.
6. Words which end in any double letters retain the double with a termination not beginning with the same letter. This rule also holds for derivatives formed by means of prefixes: e.g., agreeing, calling, recall. Exceptions: instalment, enrolment, skilful, wilful, enthralment, pontific, withal, until, and similar derivatives.
7. Words ending in -our, the u being unsounded, are spelled -or, with the exception of Saviour and glamour. The English custom is to retain the -our in most words having this ending.
8. Words derived from words ending in silent e after a consonant retain the e when the added termination begins with a consonant: e.g., state, statement, stately; pale, paleness; move, movement. Exceptions: abridgment, {35} acknowledgment, judgment, lodgment, nursling, wholly, wisdom.
When another vowel (except e or i) immediately precedes the final e, the final e is usually dropped before a consonant: e.g., argue, argument; awe, awful; true, truly, etc. There are, however, many exceptions to this rule: e.g., eye, eyesight, etc.
When the termination begins with a vowel, the final e is omitted: e.g., sale, salable; bride, bridal; force, forcible. Exceptions: mileage, etc.
9. When words end in ce or ge the final e is retained before added terminations beginning with a or o: e.g., change, changeable; courage, courageous.
10. In participles the final e is sometimes retained for the purpose of distinguishing them from other words pronounced the same but having a different meaning: e.g., singe, singeing, to distinguish from singing; dye, dyeing, to distinguish from dying, etc. The e is also retained in hoeing, toeing, and shoeing.[3]
11. Words ending in ie change their termination to y upon adding ing: e.g., die, dying; vie, vying.
12. Words ending in y preceded by a consonant change the y to i before any added termination not beginning with i: e.g., {36} merry, merriment; happy, happiness. Exceptions: adjectives of one syllable: e.g., dry, dryly; sly, slyness. Also except derivatives formed by adding ship and hood: e.g., suretyship, babyhood; but hardihood.
When the final y is preceded by a vowel, the y is usually changed to i: e.g., gay, gaiety; day, daily; pay, paid; lay, laid, etc.
13. The French ending -re in theater, center, meager, sepulcher, etc., is not now generally considered good usage.
14. The possessive of proper nouns ending in s or other sibilant is formed by adding the apostrophe and s if the word is of one syllable: e.g., James’s apple; but add the apostrophe alone if the word is of more than one syllable: e.g., For Jesus’ sake.[4]
15. Words which in their shortest form end in -d, -de, -ge, -mit, -rt, -se, -ss take the ending -sion: e.g., abscind, abscission; seclude, seclusion; emerge, emersion; admit, admission; revert, reversion; confuse, confusion; impress, impression. Other words take the ending -tion.[5]
[5] See list of irregular forms, and departures from rule on page [39.]