An Etymological Dictionary of Astronomy and Astrophysics

1. Imposing, containing, subject to, or depending on a condition or conditions; not absolute; made or allowed on certain terms.
   

2a) Logic: (of a proposition) Asserting that the existence or occurrence of one thing or event depends on the existence or occurrence of another thing or event.

2b) (of a → syllogism) Containing at least one → conditional proposition as a → premise (Dictionary.com).

2c) The “if … then” relation.

See also: → condition; → -al.