4.2 Simple, Compound, and Complex Sentences

From Clause Labels to Sentence Types

Once you can spot independent and dependent clauses, sentence types become a counting problem with a meaning check. The ATI TEAS 7 English section tests whether you can identify structures, choose the correctly formed option, and sometimes select the version that best expresses a relationship between ideas. Healthcare notes use the same toolkit: a single observation may be a simple sentence; two equal findings may be compound; a finding tied to a reason or time cue is often complex.

This section defines simple, compound, complex, and (briefly) compound-complex sentences, shows legal joining methods, and trains you to pick the structure that matches the logic—not the structure that merely "sounds longer" or more academic.

Simple Sentences: One Independent Clause

A simple sentence contains one independent clause and no dependent clause. It expresses one main idea. That idea can still include lists, modifiers, or compound parts inside the single clause.

Important distinction: Compound subjects or compound verbs do not make a sentence compound. "Compound sentence" means multiple independent clauses, each with its own subject-predicate unit that could stand alone.

• Simple (compound predicate): The patient sat up and dangled at the bedside.
• Compound (two clauses): The patient sat up, and the nurse checked orthostatic blood pressures.

Healthcare charting example (simple): "The CNA recorded intake and output at 1400." One clause, complete thought, ready for the record.

Compound Sentences: Two or More Independent Clauses

A compound sentence joins two or more independent clauses. The ideas are typically equal in grammatical weight—two findings, two actions, or a balanced contrast/result.

Legal joining methods (high-yield)

FANBOYS review: for, and, nor, but, or, yet, so. Place a comma before the coordinating conjunction when it joins two independent clauses.

Illegal join (preview of 4.3): two independent clauses with only a comma → comma splice. Two independent clauses with no punctuation or conjunction → run-on (fused sentence).

Do not force a compound comma when the second unit is not independent:

• The nurse assessed the site and changed the dressing. (simple sentence, compound predicate—usually no comma before and)

Healthcare charting example (compound): "Blood pressure remained elevated, and the nurse repeated the measurement on the opposite arm." Two complete clauses, equal narrative weight.

Complex Sentences: Independent + Dependent

A complex sentence contains one independent clause and at least one dependent clause. The dependent clause may open the sentence, interrupt it, or follow the main clause. Relative clauses also create complex sentences when they attach to a noun inside the independent clause.

Complex structure is ideal when one idea depends on another: cause, contrast, time, condition, or identification.

Meaning check:

• Equal, parallel updates → often compound: The dressing was clean, and the drain output was scant.
• Reason attached to a main fact → complex: The dressing was clean because drainage had slowed.
• Time frame for an action → complex: After the dressing change, the nurse reassessed pain.

Healthcare patient-education example (complex): "If you feel short of breath while walking, sit down and use your rescue inhaler as prescribed." The if clause sets the condition; the imperative independent clause states the action.

Compound-Complex Sentences (Brief but Recognizable)

A compound-complex sentence has at least two independent clauses and at least one dependent clause.

Example: When the saturation dropped, the nurse applied oxygen, and the patient regained a normal rate.

• Dependent: When the saturation dropped
• Independent 1: the nurse applied oxygen
• Independent 2: the patient regained a normal rate

TEAS may ask you to identify this type or to choose a correctly punctuated version. Count the independent clauses first, then check for any dependent clause. Do not confuse a long simple sentence (one clause with many phrases) with compound-complex structure.

Choosing Structure to Match Relationships

Sentence type is not only a label—it is a logic match. TEAS "most effective" or "best combines" items often hinge on this.

Worked comparison (same clinical content, different structures):

1. Simple: The nurse held the morning medications.
2. Compound: The nurse held the morning medications, and she notified the provider.
3. Complex: The nurse held the morning medications because the patient was scheduled for surgery.
4. Compound-complex: Because the patient was scheduled for surgery, the nurse held the morning medications, and she notified the provider.

None is "more correct" in the abstract. The best choice depends on what the stem asks you to emphasize and whether the grammar of the join is legal.

TEAS Classification Drills

Train yourself to annotate quickly:

1. Bracket every clause (subject + verb unit).
2. Mark each clause I (independent) or D (dependent).
3. Apply the count table above.
4. Verify punctuation for compound joins (comma + FANBOYS or semicolon—not bare commas).

Classify these (answers in parentheses):

• The infusion pump alarmed twice during the shift. (simple)
• The infusion pump alarmed twice, so the nurse troubleshot the line. (compound)
• When the infusion pump alarmed twice, the nurse troubleshot the line. (complex)
• When the infusion pump alarmed twice, the nurse troubleshot the line, and the educator observed the check. (compound-complex)
• The nurse and the educator troubleshot the line. (simple—compound subject, one clause)

Common Mislabeling Traps

Exam Strategy

When a stem says "Which sentence is complex?" hunt for a subordinating conjunction or relative clause attached to a single main clause. When it says "compound," hunt for two full sentences legally joined. When it asks which option best combines sentences, preserve the logical relationship the original ideas show—do not smash a clear cause-effect into a limp and compound if the stem highlights reason, and do not bury equal actions under an unnecessary although. Structure is a tool for clarity in nursing notes and a scoring tool on TEAS: use the type that makes the relationship obvious and the grammar legal.