isation

isation is a suffix used in English to form nouns that denote a process, result, or state derived from a verb, particularly those formed with the spelling -ise (for example, realise or organise). The resulting nouns often refer to the act of performing the verb’s action or to the system, structure, or concept that results from it, such as organisation or capitalisation.

The suffix originates from Latin -atio, passed into English via French as -isation and its American counterpart -ization. In British English, -isation is standard for many common words, while American English typically uses -ization. Examples include organisation versus organization, capitalisation versus capitalization, and socialisation versus socialization.

Not every verb yields a -isation noun form, and some terms exist primarily in -ization or -isation depending on regional conventions. Style guides emphasize consistency within a text, as switching between forms can be distracting. In practice, many speakers encounter both spellings for the same word depending on regional or institutional norms. Common pairs include realise/realisation and realise/realization, though the latter American pair is more common in U.S. writing.

Beyond English, the distinction between -isation and -ization reflects a broader British–American divergence in verb-derived nouns. Dictionaries and style guides often note preferred spellings for individual words and provide guidance to maintain uniform usage across a work.