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Is there any difference in meaning to start a two-clause sentence with "As" or "Because" in first clause to explain the reason for the second clause

As we need that function, we must import the following properties file.

Because we need that function, we must import the following properties file.


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I am reminded of a note my English professor wrote on one of my papers these thirty years ago: "Be careful using 'as' for 'because' as it may lead to confusion." And he was right- I certainly was confused as to whether he knew he'd done it there or not. – Jim Apr 12 '12 at 5:55
up vote 3 down vote accepted

Fowler in Modern English Usage states:

To causal or explanatory 'as-clauses', if they are placed before the main sentence, there is no objection.

Garner in his Modern American Usage does not fully support this, stating:

In the causal sense, 'as' should be avoided because it may be misunderstood as having its more usual meaning 'while', especially when it is placed anywhere but the beginning of the sentence.

Swan (a British grammarian) in Practical English Usage points to a subtle distinction in the meaning of the two words:

'As' and 'since' are used when the reason is already known to the listener/reader, or when it is not an important part of the sentence. 'Because' puts more emphasis on the reason, and most often introduces new information which is not known to the listener/reader.

If we follow Swan on this, then the OP's second sentence "Because we need that function, .. " places more emphasis on the need for the function, and the fact that the reader might not be aware of this, than does "As we need that function .. ".

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+1 Even at the beginning of a sentence, "as" is less clear and "because" should be used. – htoip Apr 12 '12 at 11:02
A thorough answer. Thanks. – bnguyen82 Apr 13 '12 at 9:20

Technically, in terms of meaning, both are correct. "As" can be used to show causation, "because" definitely can, and while we're at it, "since" can be used as well:

Since we need that function, we must import the following properties file.

For some reason, though, the first form (the one that uses "as") sounds less natural to the ear. It may be because I'm used to seeing "as" used to convey a sense of simultaneity, e.g.

As we were walking to the market, we came across a giant well.

Of course, this conjunction has many uses, as the dictionary definition on Free Online Dictionary shows. It definitely can be used to show causation; it's just a matter of personal preference.

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Consider: "As we need that functionality, we will implement it." Does that mean we will implement it because we need it? Or does it mean we will implement it in parts, performing each part when we need that specific part? – David Schwartz Apr 12 '12 at 9:50
Yes, as you pointed out, the fact that this preposition can lend so many different meanings to a sentence is reason enough to be cautious with its use. Interestingly, even though "as" could be used fairly unambiguously in the OP's sentence, most people will have a natural tendency to do a double-take after reading, just to eliminate other meanings. Using "because" would just make the reader's life easier. – Milind Ganjoo Apr 12 '12 at 10:04

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