the prepositional phrase 'because of' is used to indicate the reason or cause of something. It introduces the specific factor or circumstance leading to a particular result or situation.
'because of' is followed by a noun or noun phrase (or a gerund, which functions as a noun). It cannot be followed directly by a clause (a subject + verb combination).
The game was canceled because of the rain.
She was late because of traffic.
They're upset because of the decision you made.
A common mistake is confusing 'because' with 'because of.' While both indicate causation, 'because' is followed by a clause, and 'because of' is followed by a noun or noun phrase. For instance, 'He left early because he was tired.' (correct) 'He left early because of his tiredness.' (incorrect) 'He left early because of he was tired.' 'Due to' is another phrase that indicates causation and is often used interchangeably with 'because of.' However, traditionally, 'due to' is used after forms of the verb 'to be' (e.g., 'The cancellation was due to rain'). Over time, this distinction has become less strict, but it's good to be aware of it, especially in formal writing.