The document discusses the complex grammatical structure of verbs in English. It covers the different types of verbs including finite and non-finite verbs. Non-finite verbs include infinitives, participles, gerunds and verbals. It also examines the grammatical categories expressed by verbs such as tense, aspect, voice, and mood. Additionally, it analyzes the subclasses of verbs including actional, statal, modal, auxiliary, linking and semi-notional verbs.