Hierarchy relationship in data type.
Hierarchy of type
Primitive Type > Number > DOUBLE > FLOAT > BIGINT > INT > SMALLINT > TINYINT > STRING > BOOLEAN
Note that the type hierarchy allows the implicit conversion of STRING to DOUBLE.
Hierarchy of class
More generally, every type may be organised in a hierarchy using a inheritance design. Example in Java: Java - (Inheritance|Class Hierarchy) - (Subclass|Superclass) - (Extends, Super) - ( is a relationship)