Clauses: independent and dependent

Intuition [Beginner]

A clause is a group of words that contains a subject and a verb. It is the basic building block of every sentence.

There are two kinds:

1. Independent clause: Can stand alone as a complete sentence. It expresses a full thought.

   • "The rain stopped."
   • "She opened the door and walked inside."

2. Dependent clause (also called a subordinate clause): Cannot stand alone. It has a subject and a verb, but it begins with a word that makes it incomplete -- it leaves you waiting for more information.

   • "Because the rain stopped ..." (leaves you hanging: what happened?)
   • "... that she bought yesterday" (leaves you hanging: what are we talking about?)

Dependent clauses do three main jobs, depending on what they act like:

• Noun clause: Acts like a noun. "I know what she wants." (The whole clause is the object of "know.")
• Adjective/relative clause: Acts like an adjective, describing a noun. "The book that I read was excellent."
• Adverb clause: Acts like an adverb, telling when, why, how, or under what condition. "We left because it was late."

Visual [Beginner]

INDEPENDENT CLAUSE = complete thought

  [Subject]    [Verb]    [rest of clause]
   She         ate       lunch.
   -----------------------------------
   "She ate lunch."          = sentence (one independent clause)

DEPENDENT CLAUSE = incomplete thought (starts with a subordinating word)

  [Subordinator] [Subject]  [Verb]   [rest]
   because        she        was      tired
   -----------------------------------------
   "because she was tired"   = NOT a sentence by itself

COMBINING THEM:

  [Independent clause]           [Dependent clause]
   We went home         +        because she was tired
   ---------------------------------------------------
   "We went home because she was tired."  = complete sentence

Common subordinating words that start dependent clauses:

  TIME:        when, after, before, since, until, while, as
  CAUSE:       because, since, as
  CONDITION:   if, unless, provided that, whether
  CONCESSION:  although, though, even though, while
  PURPOSE:     so that, in order that
  RELATIVE:    who, whom, whose, which, that
  NOUN CLAUSE: that, whether, what, how, where, when, why

Worked example [Beginner]

Identify the clauses in each sentence.

1. "The movie ended, and we went home."

• Clause 1: "The movie ended" (independent -- complete thought).
• Clause 2: "we went home" (independent -- complete thought, joined by "and").
• Two independent clauses = a compound sentence.

2. "I stayed home because I felt sick."

• Clause 1: "I stayed home" (independent).
• Clause 2: "because I felt sick" (dependent -- begins with "because," cannot stand alone).
• One independent + one dependent = a complex sentence.

3. "She asked what I wanted for dinner."

• Clause 1: "She asked ..." (independent -- "She asked" can stand if we accept an implied object).
• Clause 2: "what I wanted for dinner" (dependent noun clause -- acts as the object of "asked").

Check your understanding [Beginner]

Formal definition [Intermediate+]

A clause is the smallest grammatical unit that can express a complete proposition. Every clause contains (at minimum) a predicate centered on a verb, and most clauses also contain a subject NP.

Clauses are classified by their ability to stand alone:

Type	Definition	Example
Independent (main)	Can function as a complete sentence	She left early.
Dependent (subordinate)	Functions as a constituent within a larger clause	because she left early

Dependent clauses are further classified by their internal function:

Function	Description	Subordinator	Example
Noun clause	Occupies a NP position (subject, object, complement)	that, whether, what, how, where, when, why	I know [that she left].
Relative/adjective clause	Modifies a noun; contains a gap co-indexed with the head noun	who, whom, whose, which, that	the book [that she read]
Adverb clause	Modifies a verb, adjective, or the entire clause; expresses circumstance	because, if, when, although, since, ...	She left [because she was tired].

Finite vs. non-finite clauses. Clauses are also distinguished by whether their verb is finite (marked for tense and/or agreement) or non-finite (infinitive, participle, or gerund). Non-finite clauses are always subordinate: "She wants [to leave]" (infinitive clause), "[Having finished] the exam, she left" (participial clause).

Complementizer. The word that introduces many subordinate clauses (that, if, whether) is called a complementizer (C). It occupies the head of the CP (complementizer phrase) projection in syntactic theory.

Key concepts [Intermediate+]

1. Subjects in dependent clauses. Dependent clauses have their own subjects, distinct from the subject of the main clause. In "She said [that he was leaving]," the dependent clause has its own subject ("he"). Some dependent clauses allow subject omission under coreference: "She said [she was leaving]" (the null subject is understood as "she").

2. Structural position. The position of a dependent clause signals its function. Noun clauses occupy argument positions (subject, object). Relative clauses follow the noun they modify (postnominal). Adverb clauses can appear sentence-initially or sentence-finally: "Because it rained, we stayed in" vs. "We stayed in because it rained."

3. Complementizers vs. subordinating conjunctions. Traditional grammar calls words like that, because, if "subordinating conjunctions." Modern syntax distinguishes complementizers (which head a CP projection: that, if, whether) from subordinating conjunctions that are better analyzed as prepositions taking clausal complements (because, before, after, since).

4. The that-trace effect. In standard English, the complementizer that cannot appear immediately before a wh-trace in subject position: "Who do you think *(that) left?" is ungrammatical with that present. This is a well-known locality constraint on movement (Chomsky & Lasnik 1977).

5. Free relatives. Some noun clauses lack an explicit antecedent: "I ate [what was on the table]." These are called free relative clauses or transparent free relatives. The wh-word (what, whoever, wherever) simultaneously functions as the subordinator and as an argument inside the dependent clause.

Linguistic theory [Master]

In X-bar theory and its descendants, clauses are analyzed as full projections of the functional categories C (complementizer) and T (tense), with a VP (or vP) complement. The structure of a finite clause is standardly given as:

      CP
     /  \
    C    TP
        /  \
      T     vP
           /  \
         v     VP

The CP level is where complementizers (that, if, whether) and moved wh-elements appear. The TP level hosts tense and subject agreement. The vP level introduces the external argument (subject) and is the locus of voice distinctions (active/passive).

Subordinate clauses come in several structural types. Finite complements are full CPs with tense. Non-finite complements include infinitivals (CP with a non-finite TP), gerunds, and participial clauses. The selection of complement type is determined by the matrix verb: believe takes both finite (believes that...) and infinitival (believes him to be...) complements, while want takes only infinitival (wants to leave, wants him to leave).

Control and raising. Infinitival subordinate clauses raise a central distinction. In "She seems [to be tired]," the subject "she" originates inside the infinitival clause and raises to the matrix subject position -- this is raising. In "She wants [to leave]," the subject "she" is base-generated in the matrix clause and controls the interpretation of the null subject (PRO) of the infinitival -- this is control. The distinction has syntactic diagnostics: raising verbs (seem, appear, happen) allow expletive subjects (It seems to be raining), while control verbs (want, try, hope) do not.

Adjunct vs. complement clauses. A fundamental distinction in clause combining is whether the subordinate clause is a complement (selected by the matrix verb, obligatory or strongly preferred) or an adjunct (optional, adding circumstantial information). Complement clauses are selected: know that S, wonder whether S. Adjunct clauses are not: "She left [because S]" -- the because-clause is not selected by left. This distinction affects constituency tests, extraction possibilities, and scopal interactions.

Tough-movement and exceptional case marking. Some subordinate clause constructions involve non-local dependencies that have been the subject of extensive theoretical debate. "John is easy [to please __]" involves a dependency between "John" and the object gap inside the infinitival. Verbs like believe allow exceptional case marking: "She believes [him to be innocent]" -- the infinitival subject "him" receives accusative case from the matrix verb, an exception to the usual clause-boundedness of case assignment.

Historical context [Master]

Subordinate clauses have been a feature of English since its earliest records. Old English used a rich system of subordinating particles (thæt, gif, hwonne, for tham the) that are the ancestors of modern that, if, when, because. The complementizer that (OE thæt) was originally a demonstrative pronoun that was reanalyzed as a clause introducer through processes of grammaticalization during the Proto-Germanic period.

The system of non-finite subordinate clauses (infinitives, participles) has expanded significantly from Old English to Present-Day English. Old English relied more heavily on finite subordinate clauses, while Modern English makes extensive use of infinitival and participial constructions. The to-infinitive developed from the Old English preposition to + a dative infinitive ending in -anne, which grammaticalized into the modern infinitive marker to.

The that-complementizer has been gradually declining in spoken English (especially American English) for centuries, a process known as that-dropping or zero complementization: "I think she left" instead of "I think that she left." This is not a new phenomenon -- it is attested from Middle English onward -- but it has accelerated in colloquial registers.

Bibliography [Master]

• Borsley, R. (1991). Syntactic Theory: A Unified Approach. Edward Arnold.
• Chomsky, N., & Lasnik, H. (1977). Filters and control. Linguistic Inquiry, 8(3), 425-504.
• Huddleston, R., & Pullum, G. (2002). The Cambridge Grammar of the English Language. Cambridge University Press.
• McCawley, J. (1988). The Syntactic Phenomena of English. University of Chicago Press.
• Noonan, M. (2007). Complementation. In T. Shopen (Ed.), Language Typology and Syntactic Description, Vol. 2. Cambridge University Press.
• Quirk, R., Greenbaum, S., Leech, G., & Svartvik, J. (1985). A Comprehensive Grammar of the English Language. Longman.