Because vs. Because Of
Because introduces a clause that gives a reason, while because of is a two-word preposition followed by a noun phrase or equivalent nominal expression. They express similar cause relationships but take different grammatical complements.
Use because before a clause; use because of before a noun phrase or similar nominal expression.
Key details
Choose the right form
| Meaning / situation | Construction | Decision |
|---|---|---|
| the reason is expressed as a finite clause | because + clause | use “because” before a subject-and-verb clause |
| the reason is expressed as a noun phrase or nominal expression | because of + noun phrase | use “because of” before the nominal reason |
Quick tests
Clause-or-noun test
Does the reason that follows have its own subject and finite verb?
If yes: Use “because” before the clause.
If no: Use “because of” before the noun phrase or comparable nominal expression.
Caveat: Longer constructions can be recast in several ways; the practical test is the grammar of the complement immediately following the linker.
Examples
We left early because the roads were closing.
“The roads were closing” is a clause.
We left early because of the road closure.
“The road closure” is a noun phrase.
The launch moved because the supplier was late, not because of the weather.
The example contrasts clause and noun-phrase complements.
Further guidance
Clause Boundary
Because introduces a subordinate clause with its own subject and verb.
Preposition Boundary
Because of behaves as a preposition and takes a noun phrase or comparable complement.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
- Because, because of and cos, cos of — Cambridge Grammar (opens in a new tab)Cambridge Dictionary · Because before a reason clause and because of as a preposition before a noun phrase