The last 20 years has seen a virtual explosion in research on children’s verb learning. This research generally shows that verbs are harder to learn than nouns (Gentner, 1982, but see Tardiff, 1996). Gentner (1982; Gentner and Boroditsky, 2001) was among the first to address why. She suggested that verbs are ephemeral, whereas nouns tend to label objects that are concrete (eg, car). Actions, on the other hand, are more abstract and fleeting, and are often labeled before or after the action has taken place (Tomasello & Kruger, 1992). Verbs are also polysemous. They tend to have multiple meanings, while nouns have more restricted meanings. For example, the Merriam-Webster Dictionary (1991) has over 40 entries for the verb “run”, but only 9 entries for the noun “ball.” In addition, objects can exist independent of actions, while actions require either an agent or object. As a result, children who hear action labels are faced with the problem of determining whether the label maps to the object or to the action. Finally, verbs can encode several components of an action, including, but not limited to, path (or the trajectory of agent; eg come, approach, enter), manner (or the way in which an agent moves; eg walk, dance, swagger, sway, stroll), result (eg open, close), and instrument (eg hammer, shovel), thus making the task of finding the referent harder.