Oxford spelling (or Oxford English Dictionary spelling) is the spelling used by Oxford University Press (OUP), including in its Oxford English Dictionary (OED), and other publishers who are "etymology conscious", according to Merriam-Webster. Apart from OUP, British dictionary publishers that use it include Cassell, Collins, and Longman. In digital documents it may be indicated by the language tag en-GB-oed.
Oxford spelling can be recognized by its use of the suffix ‑ize instead of -ise: organization, privatize and recognizable instead of organisation, privatise and recognisable. The spelling affects about 200 verbs, and is favoured on etymological grounds, in that -ize corresponds more closely to the Greek root, -izo, of most -ize verbs. The suffix -ize has been in use in the UK since the 16th century, and continues to be the spelling used in American English. Since the 1990s, -ise has become more common in the UK, with the result that -ize may be regarded incorrectly as an exclusively American variant. The OED lists the -ise form of words separately, as "a frequent spelling of -IZE...". The OED explains its use of -ize as follows:
[I]n mod.F. the suffix has become -iser, alike in words from Greek, as baptiser, évangéliser, organiser, and those formed after them from L., as civiliser, cicatriser, humaniser. Hence, some have used the spelling -ise in Eng., as in French, for all these words, and some prefer -ise in words formed in French or Eng. from L. elements, retaining -ize for those of Gr. composition. But the suffix itself, whatever the element to which it is added, is in its origin the Gr. -ιζειν, L. -izāre; and, as the pronunciation is also with z, there is no reason why in English the special French spelling should be followed, in opposition to that which is at once etymological and phonetic. In this Dictionary the termination is uniformly written -ize. (In the Gr. -ιζ-, the i was short, so originally in L., but the double consonant z (= dz, ts) made the syllable long; when the z became a simple consonant, (-idz) became īz, whence Eng. (-aɪz).)
The use of -ize instead of -ise does not affect the spelling of words in British English that end in -yse, such as analyse, paralyse and catalyse, which come from the Greek verb λύω, lyo, not from an -izo verb.
Several major newspapers and magazines in the UK use -ise. The Times had been using -ize until the early 1990s, when it decided to switch to the -ise spelling. The Times Literary Supplement has continued to use Oxford spelling. Oxford spelling is also used in academic publications; the London-based scientific journal Nature uses it, for example.
Oxford spelling is the de facto spelling standard used in style guides of international organizations that belong to the UN System, for example the World Health Organization, the International Labour Organization and UNESCO. UN treaties and declarations, such as the Universal Declaration of Human Rights follow Oxford spelling. Other international organizations that adhere to this standard include the International Organization for Standardization, the World Trade Organization, the North Atlantic Treaty Organization, the International Telecommunication Union and the International Baccalaureate Organization.
Language tag comparison 
The following table summarizes a few general spelling differences between the four major spelling systems. Note: en-GB simply stands for British English; it is not specified whether -ize or -ise should be used. The language tag en-GB-oed, however, requires the consistent use of -ize and -ization.
See also 
- Spelling differences: -ise, -ize
- Canadian English spelling
- Macquarie Dictionary (Australian usage)
- Oxford English Dictionary
- Oxford comma
- "ize", Merriam-Webster's Dictionary of English Usage. Merriam-Webster, 1994, p. 568.
- McArthur, Tom (ed.). "The -ize and -ise group", Concise Oxford Companion to the English Language. Oxford University Press, 2005, p. 124.
- Ritter, R.M. New Hart's Rules. Oxford University Press, 2005, p. 43.
- That it affects around 200 verbs, see Upward, Christopher and Davidson, George. "The suffix -IZE/-ISE", The History of English Spelling. John Wiley & Sons, 2011, p. 220.
- "Are spellings like 'privatize' and 'organize' Americanisms?". AskOxford. Oxford University Press. Retrieved 2008-07-14.
- "Questions answered, January 13, 2004". Times Online. (Internet Archive)
- "Spelling", University of Oxford Branding Toolkit.
- The spelling "analyse" is listed first, ahead of "analyze", by The Winston Canadian Dictionary, Holt, Rinehart and Winston of Canada, Toronto, 1960, 1974.
- The termination -or was formerly endorsed by the Gage Canadian Dictionary.
- The Oxford English Dictionary (1st ed.)
- The Oxford English Dictionary 2nd ed. (20 vols.)
- The Oxford English Dictionary, Oxford: Oxford University Press (latest edition: on WWW)
- United Nations Editorial Manual, New York: United Nations Publications, 1983
Further reading 
- IANA Language Tag Registration Form for en-GB-oed
- AskOxford: Are spellings like privatize and organize Americanisms?
- British Medical Journal: -ize right
- World Wide Words: The endings "-ise" and "-ize"
- Tieken-Boon Van Ostade, Ingrid. An Introduction to Late Modern English. Edinburgh University Press, 2009, p. 38.