__________ is a specific domain in the relation which has entries of all tuples.

In the context of relational databases, the term you're looking for is "attribute domain." An attribute domain refers to a specific set of values that an attribute (or column) in a relation (or table) can hold. Each attribute in a database relation may be defined with a particular domain that specifies the type of data (such as integers, strings, dates, etc.) and any constraints on what values are acceptable.

For example, if you have a table with a column for "Age," that attribute might have a domain of non-negative integers, meaning it could hold values starting from 0 and upwards. It’s critical for maintaining data integrity, as it prevents the entry of invalid data types or values that are inconsistent with the overall data scheme.

Understanding attribute domains is fundamental in designing robust and effective database schemas, as it influences how data is stored, retrieved, and managed within a database system, ensuring that the data adheres to specified formats and constraints.