This work presents a unified theory of aspect within Universal Grammar. It provides an unusual combination of syntactic, semantic, and pragmatic approaches to a single domain, and gives detailed linguistic analyses of five languages with very different aspectual systems: English, French, Mandarin Chinese, Navajo and Russian. This second edition has been completely revised to include further development of the two-component theory, including new treatments of boundedness, dynamism and a general account of aspectual shifts. It includes syntactic and semantic tests.