clause 1 + , + linker + clause 2Both sides are full clauses, so each side has its own subject and verb.
Compound Sentence
B1A compound sentence joins two full clauses with and, but, or, or so. Use a comma before the linker when both sides are complete clauses.
What you'll learn
- Join two full clauses in one sentence.
- Choose and, but, or, or so by meaning.
- Place a comma before the linker between two full clauses.
- Fix run-on sentences with two complete clauses.
Structure
Build a sentence
First clause
Linker
Second clause
Anna cooked dinner,andshe watched a movie
Anna cooked dinner, and she watched a movie.
Use and to add one full idea to another. Keep a comma before the linker.
When to use
Balanced ideas
Use a compound sentence when both parts matter equally. Each clause could be a full sentence by itself.
Addition or sequence
Use and to add one full idea to another: Maria finished the report, and Tom sent it.
Contrast, choice, result
Use but for contrast, or for a choice, and so for a result: I called him, but he didn't answer.
Markers
andbutorso
In contrast
vs complex-sentence
Compound sentence = two main clauses of equal weight. Complex sentence = one main clause plus a dependent clause.
Common mistakes
Wrong
Anna cooked dinner, and watched a movie.
Correct
Anna cooked dinner, and she watched a movie.
The second clause is also a full idea, so it needs its own subject and verb.
Wrong
Mia was tired, and she went to bed early.
Correct
Mia was tired, so she went to bed early.
Use so when the second clause is the result of the first one.
Wrong
Tom called me and I answered at once.
Correct
Tom called me, and I answered at once.
Put a comma before the linker when it joins two complete clauses.
Wrong
Lisa opened the window the room felt cooler.
Correct
Lisa opened the window, and the room felt cooler.
Two complete clauses cannot stand together with no linker or sentence break.
Common misconceptions
❝ If I use and or but, I never need a comma. ❞
When and or but joins two full clauses, use a comma before it: Sam smiled, and Eva laughed.
❝ A compound sentence works only when both clauses have the same subject. ❞
The subjects can be the same or different. What matters is that both sides are complete clauses.
Skills in this rule (5)
JOIN_TWO_FULL_IDEASw5Join two full ideas in one sentence
Use a linking word to connect two complete parts that can stand alone. Each side needs its own subject and verb.
CHOOSE_AND_BUT_OR_SOw5Choose and, but, or, or so by meaning
Use and to add, but to contrast, or to give a choice, and so to show a result. Pick the linker from the relationship between the two ideas.
COMMA_BEFORE_LINKERw4Put a comma before and, but, or, and so between two full clauses
When two complete clauses are joined in one sentence, place a comma before the linker. The comma helps the reader see the clause boundary.
AVOID_RUN_ONw5Avoid run-on sentences with two full clauses
Do not place two complete clauses together with no linker or punctuation. Add a linker with a comma, or split them into two sentences.
USE_COMPOUND_FOR_BALANCED_IDEASw3Use a compound sentence for two balanced ideas
Use this pattern when both parts have equal importance. Each clause gives a separate main point, not one inside the other.