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.