εἰμί to be versus εἶμι I'll go

 
Remember: εἶμι (to go) has a stem iota (real or subscript) in ALL of its forms,
εἰμί (to be) has no stem in either subjunctive or optative.
εἶμι (to go) has a pure iota as stem in both moods.

 

Present Subjunctive
Normal subjunctive endings: -ω. -ῃς, -ῃ, -ωμεν, -ητε, -ωσιν  
No stem for "to be", short iota stem for "to go"
so as (who?) be who? so as (who?) go
ἵνα  
ᾖς

ὦμεν  
ἦτε
ὦσιν
 I
 you (sg)
   he,she,it  
  we
 you(pl.)
  they
ἵνα  
ῇς

ῶμεν  
ῆτε
ῶσιν

 

Present Optative
Wishful thinking: If only the sun shone tomorrow!
Wishful thinking: εἴθε ὁ ἥλιος λάμποι αὔριον.
Potential fact: They could/might/would say things like that
Potential fact: λέγοιεν ἂν ταῦτα
If only ... may/will be! who? .... might/could/would go
εἴθε   εἰην
εἴης
εἴη
εἶμεν - εἴημεν  
εἶτε   - εἴητε
εἶεν   - εἴησαν
 I
 you (sg)
   he,she,it  
  we
 you(pl.)
  they
  οιμι - οίην
  οις
  οι
  οιμεν  
  οιτε
  οιεν
 ἄν