ceteris paribus

• caeteris paribus
• cæteris paribus
• cet. par.
• c.p.

New Latin cēterīs, the ablative case plural of cēterus (“the other”), + pāribus, the ablative case plural of pār (“equal”).

ceteris paribus (not comparable)

1. All other things being equal; with all other things or factors remaining the same; other things held constant; all else unchanged.
   • 1665, Robert Hooke, Micrographia:

     And therefore 'tis not to be doubted, but could we make a Microscope to have one only refraction, it would, cæteris paribus, far excel any other that had a greater number.

   • 1887, C. Barus; V[incenc] Strouhal, “The Effect of Sudden Cooling Exhibited by Glass and by Steel, Considered both Physically and Chemically”, in Report of Work Done in the Division of Chemistry and Physics Mainly During the Fiscal Year 1885–'86 (Bulletins of the United States Geological Survey; no. 42; 50th Congress, 2d session, House of Representatives Miscellaneous Documents; no. 137), volume VII, Washington, D.C.: Government Printing Office, published 1889, OCLC 881832145, page 123:

     On closer inspection it appeared that steel annealed at 100° is, cæteris paribus, more easily soluble than glass hard steel; steel annealed at 200° more easily soluble than steel annealed at 100°, and steel annealed at 360° more easily soluble than steel annealed at 200°.

Used when comparing something to something else that is different in some way but required to be the same in all other ways for the comparison to work.