- Words with ABLE and IBLE
In writing the adjectival form of certain words there are no definite rules but the following guides may be helpful. Words ending in –ation, usually take the suffix ABLE; duration, durable; adaptation, adaptable; words ending in –sion or –tion usually take the suffix IBLE; division, divisible; permission, permissible; destruction, destructible.
- Words prefixed by DIS or MIS
When the prefix DIS or MIS is added, no change is made in the original word. A double S occurs only where the original word begins with S: disappear, misdirect, dissatisfied, disrobe, misbelieve, misspelled.
- When a noun ends in Y preceded by a consonant, the plural is formed by changing Y to I and adding ES (to the singular): variety, varieties; monopoly, monopolies.
- When a noun ends in Y preceded by a vowel, the plural is formed by adding S to the singular: holiday, holidays; journey, journeys; attorney, attorneys.
- When a noun ends in O, the plural in most cases is formed by adding S to the singular: piano, pianos; ratio, ratios. Sometimes the plural is formed by adding ES to the singular: potato, potatoes; veto, vetoes.
- When a noun ends in F or FE the plural in most cases is formed by adding S to the singular: sheriff, sheriffs; plaintiff, plaintiffs; staff, staffs; safe, safes. Sometimes the plural is formed by changing F or FE to V and adding ES: knife, knives; shelf, shelves.
- The plural is formed in some nouns by a vowel change instead of by the addition of a suffix: goose, geese; man, men; mouse, mice; foot, feet.
- Some words retain their original Greek or Latin plural forms. The singular and plural forms are given here: analysis, analyses; basis, bases; phenomenon, phenomena; parenthesis, parentheses; hypothesis, hypotheses.
- Some nouns are rarely if ever used in the singular: annals, athletics, clothes, nuptials, scissors.
- In compound nouns the plural is usually added to the last member, but sometimes the first member: passerby, passersby; son-in-law, sons-in-law; coat-of-arms, coats of arms; court martial, courts martial.
- Alternative Spelling
In competition, spellings that are thought to be “American” will be accepted so long as they are recognized in the Canadian Oxford Dictionary (Second Edition) and the Oxford Dictionary of Environment and Conservation.