weekly cost of e-cigarette use

Parent class and superclasses all the way to to 'Entity'

This is an ontological definition of the entity using the standard format of specifying the parent class followed by specification of characteristics that distinguish this class from others in that class

This is optional explanatory text, elaborating on the definition and explaining how the entity should be used

This indicates whether the entity has fuzzy boundaries e.g. adolescence. In that case users of the term must precisely specify the operationalisation of the class in each usage.