A dependent (subordinate) clause has a subject and verb but cannot stand alone because it begins with a subordinating word that makes it incomplete. Adverb clauses modify verbs (Because she studied, she passed); adjective clauses modify nouns (The book that I borrowed was excellent); noun clauses function as subjects or objects (What she said surprised me). Dependent clauses must be attached to an independent clause to form a complete sentence.
Start by identifying the subordinating conjunction or relative pronoun that signals dependency. Then classify each dependent clause by function: does it modify a verb, a noun, or act as a noun itself?
An independent clause can stand alone: "She passed the exam." A dependent clause also has a subject and verb, but begins with a word that creates incompleteness — that single word tells the reader something is missing. "Because she studied" has both a subject and a verb, but "because" signals we're waiting for a result. The subordinating word is the structural signal of dependency, and identifying it is always the first step.
The three types of dependent clauses are defined by their function in the sentence — not just by what they look like, but by what job they do. Adverb clauses answer questions that adverbs typically answer: when, where, why, how, and under what conditions. They modify verbs and begin with subordinating conjunctions (because, when, although, if, since, while). In "Although it was raining, we played outside," the dependent clause tells us the condition under which the action occurred — exactly what an adverb does.
Adjective clauses (also called relative clauses) modify nouns, just as single adjectives do, but they carry richer information. They are introduced by relative pronouns: who for people, which for things, and that for either. "The book that I borrowed was excellent" — "that I borrowed" tells us which book. The test: can you replace the clause with a simple adjective? "The borrowed book" and "the book that I borrowed" are nearly equivalent in meaning, but the clause can specify rather than just characterize.
Noun clauses do the work of nouns — they can serve as subjects, objects, or complements. "What she said surprised me" — "what she said" is the subject of "surprised." "I know that he lied" — "that he lied" is the direct object of "know." These clauses are often introduced by that, what, where, whether, or wh-words functioning nominally. The most important thing to practice is spotting the subordinate clause fragment: a dependent clause written alone as a complete sentence. Whenever you see a subordinating conjunction or relative pronoun at the start of a word group, ask: where is the independent clause this attaches to? If there isn't one, it's a fragment.