Difference between "Field Specification" and "Field Domain"

I'm currently in the process of learning (Relational) Database Design based on two popular books, online tutorials and articles. Some places, when they talk about attributes constraints, they call it an **Attribute Domain**. Some other places, when they talk about attribute specification, they call it a **Field specification**. However, some other places, they say that they are both the same, but attribute domain seems to me to be part of the field specifications since by definition, attribute domain sounds like the Physical Element part of field specification: > Physical elements: Data type, Length, Decimal Places, Character support, input mask, display format What is it now?