An aspect, feature, characteristic or parameter associated with a class or an object of a given class.
{% hint style="warning" %} Disambiguation
In some programming languages, there is a significant difference between an attribute and a property (an attribute in python being a formal class member, for example), but for the the majority of the Task 43 work, they are broadly synonymous, and which is used depends on the context (for example, when writing a JSON schema you'd use the "property" terminology). {% endhint %}