Compound and complex sentences

Intuition [Beginner]

Sentences come in four types based on how many clauses they contain and how those clauses are joined:

1. Simple sentence: One independent clause. No joining.

   • "The sun set."

2. Compound sentence: Two or more independent clauses joined together.

   • "The sun set, and the stars appeared."

3. Complex sentence: One independent clause + at least one dependent clause.

   • "The sun set before we reached the campsite."

4. Compound-complex sentence: At least two independent clauses + at least one dependent clause.

   • "The sun set before we reached the campsite, but we kept walking."

The key connectors:

• Coordinating conjunctions (FANBOYS: for, and, nor, but, or, yet, so) join independent clauses to make compound sentences.
• Semicolons (;) can also join independent clauses without a conjunction.
• Subordinating conjunctions (because, although, when, if, since, while, after, before, unless, etc.) introduce dependent clauses to make complex sentences.

Visual [Beginner]

SIMPLE:       [Independent clause]
               The dog barked.

COMPOUND:     [Independent clause]  +  [Independent clause]
               The dog barked,        and the cat ran away.

COMPLEX:      [Independent clause]  +  [Dependent clause]
               The dog barked         because it heard a noise.

COMPOUND-COMPLEX:
              [Independent]   +  [Dependent]          +  [Independent]
               The dog barked,   because it heard       and the cat
                                 a noise,               ran away.

Joining methods for independent clauses:

  1. Comma + FANBOYS:      "I stayed, but she left."
  2. Semicolon:            "I stayed; she left."
  3. Semicolon + conjunctive adverb + comma:
                           "I stayed; however, she left."

Joining method for dependent clauses:

  Subordinating conjunction: "I stayed because she left."

Worked example [Beginner]

Classify each sentence by type.

1. "She opened the window."

• One independent clause. No dependent clauses.
• Type: simple sentence.

2. "She opened the window, and a cold breeze blew in."

• Independent clause 1: "She opened the window"
• Independent clause 2: "a cold breeze blew in"
• Joined by comma + "and" (FANBOYS).
• Type: compound sentence.

3. "She opened the window so that the room could air out."

• Independent clause: "She opened the window"
• Dependent clause: "so that the room could air out" (adverb clause of purpose).
• Type: complex sentence.

4. "She opened the window so that the room could air out, but her brother closed it almost immediately."

• Independent clause 1: "She opened the window" (with the dependent clause attached)
• Independent clause 2: "her brother closed it almost immediately"
• Dependent clause: "so that the room could air out"
• Two independent + one dependent.
• Type: compound-complex sentence.

Check your understanding [Beginner]

Formal definition [Intermediate+]

English sentence types are classified by clause structure as follows:

Type	Structure	Clause count
Simple	1 independent clause	1
Compound	2+ independent clauses, no dependent clauses	2+
Complex	1 independent clause + 1+ dependent clauses	2+
Compound-complex	2+ independent clauses + 1+ dependent clauses	3+

Coordination (joining independent clauses) is achieved through:

1. Coordinating conjunctions (and, but, or, nor, for, yet, so) preceded by a comma.
2. Semicolons alone or followed by a conjunctive adverb (however, therefore, moreover, furthermore, nevertheless, consequently, thus, meanwhile).
3. Asyndetic coordination (juxtaposition with no overt connector), typically marked by a colon or dash in writing.

Subordination (introducing dependent clauses) is achieved through subordinating conjunctions, which encode semantic relations:

Semantic relation	Subordinating conjunctions
Time	when, after, before, since, until, while, as, once
Cause/reason	because, since, as
Condition	if, unless, provided that, in case, assuming that
Concession	although, though, even though, whereas, while
Purpose	so that, in order that
Result	so ... that, such ... that
Place	where, wherever
Manner	as, as if, as though

Key concepts [Intermediate+]

1. Comma rules with coordinating conjunctions. When a FANBOYS conjunction joins two independent clauses, a comma precedes the conjunction. When it joins two verbs or verb phrases within a single clause, no comma is needed: "She cooked dinner and washed the dishes" (one clause, compound predicate).

2. Semicolons and independent clauses. A semicolon functions like a period between two independent clauses that are closely related in meaning. It produces a tighter connection than a period but a looser one than a comma + conjunction. Semicolons are also used to separate items in a list when those items contain internal commas.

3. Conjunctive adverbs. Words like however, therefore, moreover, consequently are not coordinating conjunctions. They require a semicolon (or period) before them and a comma after when they connect independent clauses: "It was late**;** however**,** we kept working." Using only a comma produces a comma splice: "It was late, however, we kept working."

4. Punctuation of complex sentences. When the dependent clause precedes the independent clause, a comma separates them: "Because it was late, we went home." When the dependent clause follows, no comma is typically needed: "We went home because it was late." An exception is non-restrictive adverb clauses expressing concession or contrast, which may take a comma: "We went home**, although we wanted to stay.**"

5. Sentence variety in writing. Effective writing mixes all four sentence types. A passage composed entirely of simple sentences sounds choppy and juvenile. A passage composed entirely of compound sentences sounds monotonous. Complex and compound-complex sentences allow writers to show relationships between ideas (cause, time, condition, contrast) through subordination rather than simply stringing ideas together with "and."

Linguistic theory [Master]

The classification of sentences into simple, compound, complex, and compound-complex is a pedagogical taxonomy that maps only loosely onto the syntactic structures posited in formal theory.

In Generative Grammar, all sentences are CPs. Coordination is analyzed as a symmetric structure: [CP [CP1] and [CP2]]. Some analyses treat coordination as involving a conjunctive phrase (ConjP) headed by the conjunction (Munn 1993), while others treat the conjunction as a head that takes the second conjunct as its complement and adjoins to the first (Johannessen 1998).

Subordination involves embedding one CP within another. The subordinate CP may occupy an argument position (complement clause), an adjunct position (adverbial clause), or a specifier/modifier position (relative clause). From a formal perspective, the independent/dependent distinction is better understood as matrix vs. embedded: the matrix clause is the highest CP, and subordinate clauses are CPs embedded within it.

Asymmetry of coordination. Despite the appearance of symmetry ("A and B" seems to treat A and B equally), coordinate structures exhibit asymmetries. In "She went to the store and bought milk," the second conjunct is temporally and causally dependent on the first. Culicover and Jackendoff (1997) argue that such "subordinating conjunctions" reveal that the boundary between coordination and subordination is not sharp.

Right-node raising and gapping. Coordinate structures allow phenomena that challenge simple phrase-structural analyses. Right-node raising: "She likes, but he hates, [classical music]" -- the object "classical music" is shared across two clauses but physically appears only once. Gapping: "She likes classical music, and he __ jazz." -- the verb is elided from the second conjunct. These phenomena have been central to debates about the syntax-discourse interface.

Parataxis and hypotaxis. The typological tradition distinguishes parataxis (clauses joined without explicit subordination, like asyndeton or mere juxtaposition) from hypotaxis (explicit subordination via complementizers and subordinating conjunctions). Matthiessen and Thompson (1988) argue that the clause-combining hierarchy (coordination < subordination < complementation) correlates with degrees of integration: more tightly integrated clauses (complements) are more grammatically constrained, while less integrated ones (adjuncts, paratactic clauses) retain more clause-internal freedom.

Historical context [Master]

Old English prose relied heavily on parataxis -- clauses strung together with and (ond) with relatively little subordination. Subordinate clause constructions existed (thæt-clauses, gif-clauses, thonne-clauses) but were less frequent than in Modern English. Long sentences with multiple layers of subordination were characteristic of Latin, not of early Germanic prose.

The influence of Latin through the Church, law, and scholarship gradually increased the use of subordinate clauses in English writing. By the Early Modern English period, writers like Sir Thomas Browne and Samuel Johnson produced famously long, heavily subordinated sentences that would have been unrecognizable in Old English.

The 20th century saw a reaction against this complexity. Hemingway's style -- short, predominantly simple and compound sentences -- became influential in both literature and journalism. Contemporary academic writing occupies a middle ground, using complex sentences for precise logical relationships while avoiding the extreme subordination of 18th-19th century prose.

Bibliography [Master]

• Culicover, P., & Jackendoff, R. (1997). Semantic subordination despite syntactic coordination. Linguistic Inquiry, 28(2), 195-217.
• Dik, S. (1968). Coordination: Its Implications for the Theory of General Linguistics. North-Holland.
• Huddleston, R., & Pullum, G. (2002). The Cambridge Grammar of the English Language. Cambridge University Press.
• Johannessen, J. (1998). Coordination. Oxford University Press.
• Matthiessen, C., & Thompson, S. (1988). The structure of discourse and "subordination." In J. Haiman & S. Thompson (Eds.), Clause Combining in Grammar and Discourse. John Benjamins.
• Munn, A. (1993). Topics in the Syntax and Semantics of Coordinate Structures. PhD dissertation, University of Maryland.