Every distinct wording since 2010, newest first.
July 12, 2019 · Core Set 2020
An ability can be an activated or triggered ability on the stack. This kind of ability is an object. (See section 6, “Spells, Abilities, and Effects.”)
February 1, 2010 · Worldwake
An activated ability is targeted if it identifies something it will affect by using the phrase "target [something]," where the "something" is a phrase that describes an object, player, or zone. The target(s) are chosen as the ability is activated; see rule 602.2b.