ordered pair

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A pair of numbers that come in a specific order and are usually written in parentheses, such as (3, 5).

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun set theory A set containing exactly two elements in a fixed order, so that, when the elements are different, exchanging them gives a different set. Notation: (a, b) or .