I am a little bit confused in meaning of "as" and "because of". there are two sentences:

I felt tired today as I worked hard yesterday.

I felt tired because of I worked hard yesterday or I felt tired because of working hard.

Do those sentences have same sense?

i have suspense in second sentence. Is that correct? I am unable to understand second sentence as I am not native speaker of English.

Can anybody tell me about usage of because of and as?


"I felt tired today as i worked hard yesterday." is fine.

Correct usage of "I felt tired because of i worked hard yesterday" would be : I am feeling tired today because I worked very hard yesterday.

I would like to emphasize that "because of" won't be a substitute of "AS".

You can use the following for "AS" :


These differ based on the information you already have :

AS, SINCE generally come in the beginning of sentences. Also, they are used when the reason is already known to the listener/reader, or when it is not the most important part of the sentence.

As he wasn't ready, we went without him. Since she wanted to pass her exam, she decided to study well.

BECAUSE and FOR come in the middle of the sentences as conjunctions : BECAUSE often introduces new information which is not known to the listener/reader. It puts more emphasis on the reason.

We use a FOR-clause when we introduce new information. A for-clause often expresses an inference.

I read because I like reading. I decided to consult a doctor for I was feeling bad.

  • Thank you for showing your interpretation. I want to know about the because of usage. – user72862 May 22 '14 at 10:40
  • Because of is always followed by a noun or pronoun ,whereas you will always need to put a whole reason after the because clause. It could be many things. Please see the example below : We couldn’t go out because it rained. We couldn’t go out because of the rain. – Veronica Diamond May 22 '14 at 10:58
  • Ok but you know, there are two sentences, one of which is followed by a pronoun. – user72862 May 22 '14 at 11:04
  • Yes the because of one. Because of "the rain" – Veronica Diamond May 22 '14 at 11:12
  • are you talking about one of your sentences which has a pronoun? – Veronica Diamond May 22 '14 at 11:20

Both 'because' and 'as' can be used, but you would say 'I felt tired because I worked hard' omitting the of after because.