A single consonant following a single vowel and ending in a monosyllable or a final accented syllable is doubled before a suffix beginning with a vowel.
- bag, bagging
- format, formatting
- input, inputting
- red, reddish
- rob, robbing
- transfer, transferred
- but
- total, totaled, totaling
- travel, traveled, traveling
If the accent in a derivative falls upon an earlier syllable than it does in the root word, the consonant is not doubled.
- refer, reference
- prefer, preference
- infer, inference
The indefinite article a is used before a consonant and an aspirated h; an is used before a silent h and all vowels except u pronounced as in visual and o pronounced as in one.
- a historic occasion
- a hotel
- a human being
- a humble man
- a union
- an herb seller
- an hour
- an honor
- an onion
- an oyster
- but
- an H-U-D directive
- a HUD directive
When a group of initials begins with b, c, d, g,j, k, p, q, t, u, v, w, y, or z, each having a consonant sound, the indefinite article a is used.
- a BLS compilation
- a CIO finding
- a GAO limitation
- a UFO sighting
- a WWW search
When a group of initials begins with a, e,f, h, i, I, m, n, o, r, s, or x, each having a vowel sound, the indefinite article an is used.
- an AEC report
- an FCC (ef) ruling
- an NSC (en) proclamation
- an RFC (ahr) loan
Use of the indefinite article a or an before a numerical expression is determined by the consonant or vowel sound of the beginning syllable.
- an 11-year-old
- a onetime winner
- a III (three) group
- an VIII (eight) classification
- a IV-F (four ef) category (military draft)
- a 4-H Club
