ë is the characteristic vowel of the future tense for 3rd conjugation verbs - 3rd conjucation verbs DO NOT use the tense marker "bi"
Drop 'ere' from
the Present Infinitive and add ë plus endings
e.g. scrïb/ere plus 'ë' plus 's' = 2nd singular - scrïbës
Exceptions are in the usual characters: 1st singular (scrïbam), 3rd sing and pl - where the vowel in the ending is never long (scrïbet and scrïbent)
3rd Conjugation - Future