As the god Apollo says at I.05.441–442, the immortals as a ‘grouping’, phūlon, are different from mortals as a ‘grouping’, phūlon. So, he goes on to say, immortals and mortals are not the same. In the Greek, the ‘grouping’ of immortals and mortals is not homoio-, I.05.441. In terms of this negative context, then, the meaning of homoio- can be interpreted to be ‘the same as’. Meanwhile, the meaning of this same word homoio- in non-negative contexts can be interpreted to be ‘similar to’. In non-negative or let us say positive contexts, homoio- exemplifies the making of comparisons in the form of metaphors and similes.
In the case of metaphors, Aristotle himself actually uses the word homoio- in his own definition of metaphor, Poetics 1459a5–8:
πολὺ δὲ μέγιστον τὸ μεταφορικὸν εἶναι. μόνον γὰρ τοῦτο οὔτε παρ’ ἄλλου ἔστι λαβεῖν εὐφυΐας τε σημεῖόν ἐστι· τὸ γὰρ εὖ μεταφέρειν τὸ τὸ ὅμοιον θεωρεῖν ἐστιν
But the greatest use of words is the use of metaphor [tò metaphorikon ‘that which is transferable’]. This is the only thing that cannot be learned from someone else; and it is also a sign [sēmeion] of a-good-quality-that-is-inborn [euphuia], since the making of good metaphors [eu metapherein ‘good transference’] is the same thing as the contemplation [theōreîn] of what is similar [homoion] to what.
What follows is epitomized from MoM 2§§6–7. Now we turn to similes. This term simile is derived from the neuter form of the Latin adjective similis meaning ‘similar’, from which the English word similar is in turn derived. In English, a simile is signaled by expressions such as like or as or similar to. As for Greek, the primary word for signaling a simile is homoio- in the sense of ‘similar to’. But the etymology of homoio- shows that the meaning ‘similar’ derives from a more basic meaning, ‘same as’. From the standpoint of Indo-European linguistics, the Greek adjective homoio- (ὁμοῖο-) derives from homó- (ὁμό-) ‘same as’, which in turn derives from a prototypical form *somo-, meaning ‘same as’. The English adjective same is derived from this same prototypical form. Another derivative is the Latin adjective similis, meaning ‘same as’ or ‘similar to’. In the usage of both Latin similis and Greek homoio- (ὁμοῖο-), the same semantic principle applies: for A2 to be similar to A1, it has to be the same as A1 in some respect, which is X. Further, for A2 to be the same as A1, it has to be one with A1 in respect to X. That is because the Indo-European root *som- of *somo- ‘same as’ means ‘one’, as we see in such forms as the Latin adverb semel ‘one time’. And the idea of ‘one’ in words like English same has to do with an act of comparing. When we compare things, what is the ‘same as’ something else in some respect becomes ‘one with’ that something in that respect. That is how a word like Latin similis, deriving from the concept of ‘one’, means ‘similar to’ in the sense of ‘one with’. What is similis ‘similar’ to something else in some respect is ‘one with’ that something in that respect. Similarly in the case of the Greek adjective homoio- (ὁμοῖο-), it refers to something that is ‘one with’ and therefore ‘the same as’ something else in some respect. And, as we will see in the comment on O.16.172–212, if something else is not the same, then it is alloio- (ἀλλοῖο-) ‘a different kind’, which is the opposite of homoio- (ὁμοῖο-) or ‘the same kind’. As we will also see in that same comment, the extension -io- (-ιο-) of the two adjectives homoio- (ὁμοῖο-) ‘the same kind’ and alloio- (ἀλλοῖο-) ‘a different kind’ is parallel to the extension -io- (-ιο-) of the adjectives hoio- (oἷο-) ‘what kind’ and toio- (τοῖο-) ‘that kind’.
Here we loop back to what the god Apollo says at I.05.441–442: in a negative sense, immortals cannot be the same as mortals. Still, in a special positive sense, mortals can momentarily become the same as immortals when their identities merge in contexts of ritual. Such a special positive sense applies in situations of ritualized antagonism between immortal and mortal. In such situations, the mortal becomes one with the immortal—and can die as a consequence. That is what almost happens to Diomedes, but then he backs off.