Mutatis mutandis, Latin literal meaning "with those things having been changed which need to be changed" or more simply "the necessary changes having been made". The term is used when comparing two situations with a multiplicity of common variables set at the same value, in which the value of only one variable is allowed to differ—"all other things being equal"—thereby making comparison easier. It carries the connotation that the reader should pay attention to the corresponding differences between the current statement and a previous one, although they are analogous. This term is used frequently in economics and in law, to parameterize a statement with a new term, or note the application of an implied, mutually understood set of changes. The phrase is also used in the study of counter-factuals, wherein the requisite change in the factual basis of the past is made and the resulting causalities are followed.

Examples

• A local chapter of a national organization may adopt a rule that the national organization's procedure for something will apply, mutatis mutandis, to the local chapter. Thus, even though the chief officer of the national organization may be called the "president", and the chief officer of the local chapter may be called the "chairman", instances of "president" would be changed to "chairman" when applying the national procedure. This is commonly done by subordinate units (such as localities or chapters) to avoid duplication of text in local ordinances or rules that is sufficiently covered by state or national laws or rules.
• "His cat" and "His dog" should be changed to "Her cat" and "Her dog", mutatis mutandis for pony, sheep and cow. [I.e. "His pony" becomes "Her pony", and so on.]
• What we said about oil goes mutatis mutandis for natural gas.
• The two parties finally signed the contract mutatis mutandis.
• 1982 Convention in Jamaica (The law of the sea), ARTICLE 111: Section 2. The right of hot pursuit shall apply 'mutatis mutandis' to violations in the exclusive economic zone or on the continental shelf, including safety zones around continental shelf installations, of the laws and regulations of the coastal State applicable in accordance with this Convention to the exclusive economic zone or the continental shelf, including such safety zones.
• Mutatis mutandis a corpse decomposes much faster in air than in water.

Etymology

Both "mutatis" and "mutandis" come from the Latin verb "muto" (principal parts: muto, mutare, mutavi, mutatus), meaning "to change." "Mutatīs" is the ablative plural neuter perfect passive participle in its adjectival function ("having been changed"), and "mutandīs" is the ablative plural neuter gerundive used as a substantive (the neuter plural functions as "the things" and the gerundive supplies the idea of necessity in the translation—"which need to be changed"). The phrase is an ablative absolute construction, which is reflected by the "with" translation.

Quote

"We can in fact only define a weed, mutatis mutandis, in terms of the well-known definition of dirt—as matter out of place. What we call a weed is in fact merely a plant growing where we do not want it."—E.J. Salisbury, The Living Garden, 1935

See also

• Ceteris paribus ("other things being equal", semantically similar to "Mutatis mutandis")
• List of Latin phrases