Ceteris paribus (ce·ter·is par·i·bus) adv.' Abbr. cet. par.
With all other factors or things remaining the same.
Ceteris paribus is a Latin phrase, which has a literal translation of "with other things the same". However, it also loosely means "all other things constant", ""all other things being equal", or "holding all else constant". In economic terms, this phrase simply means that only factors mentioned as changed are changed; all others remain constant. Even though one thing changes, we assume everything else is still the same. This allows economists to eliminate other variables that could have an effect on a relationship between specific things, so that only the relationship between those things could be studied. Ceteris paribus makes it easier to analyze economic situations because there are nowhere near as many things to take into consideration.
An example of ceteris paribus can be found in this statement regarding the demand for cell phones:
"If the price of cell phones decreases, ceteris paribus, the quantity of cell phones demanded by consumers will stay the same."
While one realistically would factor in reception areas, the quality of the given phone(s), and whether they would rather buy an iPod or not, ceteris paribus ignores these other factors. Ceteris paribus is one of the key assumptions affiliated with economics.