Whereas a primitive is a word defined by the system, a name is a word defined by you. The primitive =. defines a name.
v =. 23
The sentence can be read as v is 23. The word =. is called copula (another good English language term). The name v is defined as the number 23 and can be used in other sentences.
5 + v 28
Unlike a primitive, a name can be redefined.
v =. 45 5 + v 50
The system does not display the result of the sentence when it begins with a copula. A sentence that contains only a name shows a display form of the definition of the name.
abc =. 123 abc 123
You can give anything a name. For example, you could give a name to the verb + .
plus =. + 23 plus 45 68
The preferred way to read abc =. def is: abc is def or abc is defined as def. However, borrowing from other computer languages, it is also common to say: abc is assigned the value def or the value def is assigned to abc.