Mutatis mutandis is a Medieval Latin phrase meaning "with things changed that should be changed" or "once the necessary changes have been made". It remains unnaturalized in English and is therefore usually italicized in writing. It is used in many countries to acknowledge that a comparison being made requires certain obvious alterations, which are left unstated. It is not to be confused with the similar ceteris paribus, which excludes any changes other than those explicitly mentioned. Mutatis mutandis is still used in law, economics, mathematics, linguistics and philosophy. In particular, in logic, it is encountered when discussing counterfactuals, as a shorthand for all the initial and derived changes which have been previously discussed. Latin The phrase —now sometimes written to show vowel length—does not appear in surviving classical literature. It is Medieval Latin<ref name=oed>Oxford English Dictionary, 3rd ed. 'mutatis mutandis, adv.''' Oxford University Press (Oxford), 2003.</ref> in origin and the Feet of fines, kept at The National Archives (United Kingdom), contains its first use in England on January 20, 1270, at Pedes Finium, 54 Hen. III, Salop. Both words are participles of the Latin verb ('to move; to change; to exchange'). is its perfect passive participle ('changed; having been changed'). is its gerundive, which functions both as a future passive participle ('to be changed; going to be changed') and as a verbal adjective or noun expressing necessity ('needing to be changed; things needing to be changed'). The phrase is an ablative absolute, using the ablative case to show that the clause is grammatically independent ('absolute' literally meaning 'dissolved' or 'separated') from the rest of the sentence. EnglishMutatis mutandis was first borrowed into English in the 16th century, but continues to be italicized as a foreign phrase. Although many similar adverbial phrases are treated as part of the sentence, mutatis mutandis is usually set apart by commas or in some other fashion. The nearest English equivalent to an ablative absolute is the nominative absolute, so that a literal translation will either use the nominative case ("those things which need to be changed having been changed") or a preposition ("with the things needing to be changed having been changed"). More often, the idea is expressed more tersely ("with the necessary changes") or using subordinating conjunctions and a dependent clause ("once the necessary adjustments are made"). The phrase has a technical meaning in mathematics where it is sometimes used to signal that a