As-Long-As-So-Long-As | Commonly Confused Words

As long as

/æz lɒŋ æz /

As long as is used to express a condition where something happens provided another thing takes place

/səʊ lɒŋ æz /

It means if or provided that a condition is met

As long as is often used to indicate duration, emphasizing the continuation of something while a certain condition is met.
Remember as long as as indicating equality in extent or condition, literally focusing on the length of time something will continue.
So long as can also mean provided that, focusing more on the condition necessary for something else to happen.
Think of so long as as referring to conditional terms like a promise or an agreement where a certain condition must be fulfilled.
Both phrases can often be interchangeable, but so long as tends to have a slightly more formal tone compared to as long as.