Some words have both preposition and conjunction forms. Confusing them is a common error for learners.
The Key Difference
A preposition is followed by a noun phrase (a noun, pronoun, or gerund). A conjunction is followed by a clause (subject + verb).
| Preposition (+ noun) | Conjunction (+ clause) | | -------------------- | ------------------------- | | Before dinner | Before I eat dinner | | After the movie | After the movie ended | | Since Monday | Since I arrived |
Because of vs. Because
Because of = preposition (followed by a noun). Because = conjunction (followed by a clause).
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Because of the rain, we stayed inside. (rain = noun)
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Because it was raining, we stayed inside. (it was raining = clause)
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Because of the traffic, I was late. (noun)
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Because there was traffic, I was late. (clause)
During vs. While
During = preposition (followed by a noun). While = conjunction (followed by a clause).
- She fell asleep during the movie. (movie = noun)
- She fell asleep while watching the movie. (watching = gerund in a reduced clause)
- She fell asleep while the movie was playing. (the movie was playing = clause)
Despite vs. Although
Despite = preposition (followed by a noun or gerund). Although = conjunction (followed by a clause).
- Despite the rain, we went out. (noun)
- Despite raining, we went out. (gerund)
- Although it was raining, we went out. (clause)
Since / For
Since can be a preposition (since Monday) or a conjunction (since I arrived). For is usually a preposition (for three hours).
- I have been here since morning. (preposition)
- I have been here since the sun rose. (conjunction)
- I have been here for three hours. (preposition)
Till / Until
Both can be prepositions or conjunctions.
- Wait till tomorrow. (preposition)
- Wait till I arrive. (conjunction)
Comparison Table
| Word | As Preposition (+ noun) | As Conjunction (+ clause) | | -------------------- | --------------------------- | ------------------------------------- | | because of / because | Because of the delay... | Because we were delayed... | | during / while | During the meeting... | While the meeting was going on... | | despite / although | Despite the rain... | Although it rained... | | since | Since last week... | Since I arrived here... | | before | Before class... | Before class starts... | | after | After lunch... | After I eat lunch... |
Common Mistakes
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Incorrect: Because the traffic, I was late.
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Correct: Because of the traffic, I was late. (noun follows)
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Incorrect: During I was sleeping, the phone rang.
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Correct: While I was sleeping, the phone rang. (clause follows)
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Correct: During my sleep, the phone rang. (noun follows)
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Incorrect: Although the rain, we played soccer.
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Correct: Despite the rain, we played soccer. (noun follows)
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Correct: Although it rained, we played soccer. (clause follows)