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Endings beginning with vowels

The endings -able, -ion, -er, -or, -ance, -ence, -ous, -ish, and -al are generally used to form adjectives and nouns. Here are some guidelines about how they affect the spelling of the word to which they're added:

  • When you're adding one of these endings to a word that ends with a consonant, the spelling is often straightforward:

adapt, adaptable

addict, addiction

mountain, mountainous

black, blackish

  • If you add one of the endings to a word that ends in an e that isn't pronounced, drop this final e:

inflate, inflation

advise, advisable

dance, dancer

The exceptions to this rule are words that end with a ‘soft’ ce or ge sound:

notice, noticeable

courage, courageous

advantage, advantageous

  • When you add one of these endings to verbs ending in a vowel plus l, you need to double the l:

counsel, counsellor

excel, excellent

  • Double the final consonant when adding these endings to verbs that end with a single vowel plus a consonant, when the stress is at the end of the verb:

refer, referral

begin, beginning

forget, forgettable

  • Don't double the final consonant, if the word ends with a single vowel plus a consonant, and the stress is not at the end of the word:

visit, visitor

common, commoner

develop, developer

  • If the word only has one syllable and ends with a single vowel plus a consonant, double the final consonant:

stop, stoppable

dim, dimmer

rob, robber

  • Don't double the final consonant if the verb ends with two vowels plus a consonant:

sleep, sleeper

treat, treatable

clean, cleanish

  • In British English, when you add the endings -ous, -ious, -ary, -ation, -ific, -ize, and -ise to a word which ends in -our, you need to change the -our to -or before adding the ending:

humour, humorous

glamour, glamorize

labour, laborious

But when you are adding other endings, the -our spelling stays the same:

colour, colourful

favour, favourite

odour, odourless

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Grammar and usage