single-valued attribute
Technical term in computing and data modeling for an attribute that holds only one value per entity.
In this database, the customer's phone number is defined as a single-valued attribute.
多値属性 (multi-valued attribute) is the opposite, allowing multiple values for a single entity.
Compound of 単一 (single) + 値 (value) + 属性 (attribute), a direct translation of the English computing term.