There are different types of definitions. We use them in different ways.
Lexical: dictionary definition, meaning of the word as it is commonly used
Practical (or stipulative): when a word is given a definition specifically for the argument in process. This is when you would say, “Okay, we’ll say that x is whatever.” X may not actually be that limited or even mean that at all, but “for the sake of the discussion” we will all agree to use it that way.
Precising: makes the definition more specific than the dictionary definition, usually by including parameters that narrow the definition. These are often used when vagueness is not acceptable (like in a legal document or a scientific document).
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