Adding Endings to Words that End in “-our”

In British English, when you add the endings -ous, -ious, -ary, -ation, -ific, -ize, or -ise to a noun that ends in -our, you need to change the -our to -or. For example:

  • humour / humourous
  • glamour / glamorous
  • labour / laborious

But when you add other endings, the -our spelling stays the same.

For example:

  • colour / colourful
  • favour / favourite
  • odour / odourless

Adapted from: Oxford Dictionaries: Spelling Rules and Tips (

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