‘As Long As’ or ‘So Long As’ … What’s the Difference?

man presents giftIs there a grammar rule that applies to as long as and so long as?

Which of these do you consider correct?

“He can join us as long as he brings a gift to exchange.”
“He can join us so long as he brings a gift to exchange.”

When using as long as or so long as to imply something conditional — He can join us if he brings a gift to exchange — both are correct.

But the three-word phrases are not interchangeable in all constructions. Here are five ways to use as long as:

1) conditional: on the condition that, providing / provided that, if

She will forgive you, as long as / so long as you apologize.
You can stay with us, as long as / so long as you don’t smoke indoors.
We will pick you up, as long as / so long as you let us know your arrival time.

2) time or duration: for the amount of time that

He can stay with us as long as he needs to.
You can use my computer as long as yours is in for repair.
I’ll remember her compliment for as long as I live.

3) reason: because

As long as your computer isn’t fixed yet, you can borrow mine.

As long as you have an appointment in the same building, let’s ride together.
As long as your clothes are here, you can stay with us this week.

4) lengths and comparisons: distance and time

The snake was as long as my arm.
Today’s movie lasted as long as last night’s play.
Saturday’s wait was as long as any I’ve experienced.

5) emphasis

She can hold her breath for as long as two minutes!
He is known to speak for as long as three hours.
Conducting research for a blog can take as long as writing it.

So now you know: You can be reassured that choosing as long as is a safe choice in most cases, thanks to its multiple meanings.

Are there other everyday phrases that make you pause to think, “Am I using this right?”

Please let me know. If you have questions, others most likely do as well.

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Kathy Watson

Kathy Watson has a love/hate relationship with grammar; she loves words and the punctuation that helps them make sense, yet she hates those pesky rules. A self-proclaimed ruthless editor, she prefers standard usage guidelines of The Associated Press Stylebook. Her easy-to-use Grammar for People Who Hate Rules helps people write and speak with authority and confidence. She encourages and welcomes questions and comments. (Email)