Sometimes, the definition of a word is pretty hard to dispute. For example, the meaning of “iron” is, unless it is used metaphorically, pretty straightforward. So is the definition of “ion”, or “book”, or “supper”. Of course, very little of interest is said to do with this. People tend not to dispute whether some food is supper, whether something is made of iron, whether some ion is present in some compound, or whether so-and-so object is a “book”; they simply look at it, and then say, “Ah, yes, it is a book” or, “Oh, no, it’s not a book.” What …