Ambiguity is doubtfulness; doubleness of meaning.

Explanation

(English-origin maxim.) Ambiguity exists wherever language is susceptible of two or more reasonable meanings — it is doubtfulness or doubleness of sense that opens the door to construction.

Where this applies

• A contract says the seller will deliver "the product" but the seller manufactures three different products — the word "product" is ambiguous because it could reasonably refer to any of them.
• A deed grants "the property on Main Street" to a buyer, but the grantor owns two lots on Main Street — there's a genuine doubleness of meaning that must be resolved.
• An insurance policy covers "accidents" but doesn't define whether that includes the policyholder's own negligence — the term is ambiguous because it can reasonably be read either way.