The many alternative forms one sees are convenient for the epic poets in their oral
composing of the lines.

Epic εἰμί (= to be)

εἰμί ἐσσ(ί), εἴς, εἶς ἐστίν εἰμέν ἐστέ ἔασ(ιν), εἰσ(ίν)
					ἐών ἐόντος ἐόντι ἐόντα ἐόντες, ὄντες ἐόντων ἐοῦσιν ἐόντας, ὄντας	ἐόν ἐόντος ἐόντι ἐόν ἐόντα ἐόντων ἐοῦσιν ἐόντα	ἔοῦσα ἔούσης, οὔσης ἐούσῃ ἐοῦσαν ἐοῦσαι ἐουσῶν ἐούσαις ἐούσας
	ἔω ἔῃς(θα) ἔῃ,εἴῃ,ἔῃσι, ᾖσι ἔωμεν ἔητε ἔωσιν, ὦσιν	εἴην εἴης, ἔοις εἴη, ἔοι εἴμεν εἴτε εἴεν	ἔσσο ἔστω ἔστε ἔστων
				ἔμ(μ)εν(αι)/ εἶναι
ἦα, ἔα, ἔον ἦσθα, ἔησθα ἦεν,ἔην,ἦν,ἤην,ἔσκε ἦμεν ἦτε ἦσαν,ἔσαν,εἴατο

It will be noted that ἔσσο is a M-form inserted into the A.

dual forms: ἔστον, ἤστην

future: ἔσ(σ)ομαι; ἔσ(σ)εαι/ἔσῃ; ἔσ(σ)εται/ἔσται/ἐσσεῖται; ἐσσόμεθα/ἐσόμεσθα; ἔσεσθε; ἔσ(σ)ονται; ἔσεσθον; ἔσ(σ)εσθαι; ἐσσόμενος.