Usage is the best interpreter of things.

Explanation

When the meaning of a term or provision is doubtful, how it has been understood and applied in practice is the strongest evidence of its true sense.

Where this applies

• Nobody agrees on what a term means so we should look at how it's actually been used in practice.
• The best way to understand a vague contract term is to see how the parties have been applying it.
• We've been interpreting this provision the same way for years — that usage should control.

See also

• 10.1.9 Contemporaneous exposition is the best and most powerful in law.