What's the Dif? (Vol. 1): Because or Since?

There is a lot of confusion about these two. Which should you use? Which is better? On Grammar Girl's FB group, someone just mentioned that, in law school, she was taught to never use since to mean because. Since should only be used to describe length of time, or how long something has continued. I understand this and it's probably not a bad rule of thumb, especially in the law where nuance can be left open to so much interpretation.

If you want to keep it simple, follow this rule. It's a good one. However, if you want to know the difference, perhaps this will help.

As I mentioned above, since has two uses. The first is to describe length of time. It describes something that began in the past and is still continuing now. When you use since in this way, you must ALWAYS use the simple past tense in the adverb clause with since, and you must ALWAYS the present perfect tense in the main clause. There is no other pattern that I am aware of. For example:

• I have lived in Hawaii since I returned to the US from Japan in 2001.
• Jenny has wanted to be a dancer since she was a very little girl.

The second use of since is in cause and effect sentences and has the same meaning as because. However, there is a fairly significant difference between the two. Which to use depends on what information is most important. What do you want to emphasize? Take the following sentences as an example.

• We decided to come home from the beach early because the children were really tired.
• Since the children were tired, we decided to come home from the beach early.

Both of these sentences have the same meaning, but in the first sentence, the most important information is why we came home early. That's why it is at the end of the sentence. On the other hand, the most important information in the second sentence is the result, or effect, of the children's tiredness, i.e. coming home early.

The simplest way I can explain the difference is this: If the cause (reason) is the more important than the effect (result), the use because and put it in the middle. If the effect (result) is more important than the cause (reason), then use since and put it at the beginning.

A second way to explain this is: Because goes in the middle of the sentence and since goes at the beginning. Never begin a sentence with because and never put since in the middle.

• because = important = in the middle
• since = less important = at the beginning

Or, follow the really simple rule and only use since to explain how long.