Learn English – “So long as” vs. “as long as”

conjunctionsformalityso-vs-asword-choicewriting-style

Which phrase is more formal — "so long as" or "as long as"?

Example:

  • So long as Google Voice allows free long distance in North America, I will use it.
  • As long as Google Voice allows free long distance in North America, I will use it.

I'm leaning toward 'as long as' but I have no justification.

Best Answer

I don't know that the distinction between these two is formality. I think that "so long as" indicates a logical predication, and "as long as" indicates a specific time interval. Take your two examples.

  • So long as Google Voice allows free long distance in North America, I will use it.

I think this could be paraphrased as

  • My use of Google Voice is conditional upon free long distance calls in North America.

Your second example was

  • As long as Google Voice allows free long distance in North America, I will use it.

This could be paraphrased as

  • For the duration of time that Google Voice allows free long distance in North America, I will be using it.

Thinking about it, I think that both "so long as" and "as long as" are used for the conditional reading, but only "as long as" can be used for the duration reading.