Aristotle has just finished saying how differences in definition can indicate multiple meanings. Now he continues his discussion of the second tool by showing that comparisons can also indicate multiple meanings. He does this in Topics, Book 1.
Moreover, see if the terms cannot be compared as more or less or as in like degree, as is the case (e.g.) with a clear sound and a clear argument, and a sharp flavour and a sharp sound. For neither are these things said to be clear or sharp in a like degree, nor yet is the one said to be clearer or sharper than the other. Clear, then, and sharp are homonymous. For synonyms are always comparable- for they will always hold either in like manner, or else in a greater degree in one case.
We can also try to compare various uses of a word with each other. For example, we can compare a clear sound with a clear argument and ask which one is clearer. If the word clear has a single meaning, then this kind of comparison is sensible. Since we cant compare these items, they do not have the same meanings. Another example is sharp flavor and sharp sound. Which one is sharper? Neither, as the question makes no sense. Therefore, sharp means different things. You can always compare words if they mean the same thing.
Next, Aristotle discusses differentia.