Envelope begins and ends with the letter e. It contains one letter.
A word that begins and ends with E and has only 1 letter in between is EYE. Begins and ends with E and the Y is in between.
moonbeam
Critic.
If the question means 'one other letter', I believe the answer is eye. (Adds one letter Y.) If the question is a riddle, the answer is 'envelope' as it begins and ends with 'e', and it contains a letter.
Envelope
A word that begins and ends with E and has only 1 letter in between is EYE. Begins and ends with E and the Y is in between.
Ergosterol, for one.
E
long is one :)
moonbeam
One word is Madam.
Ballerina is one 9-letter word beginning with B and ending with A.
Critic.
If the question means 'one other letter', I believe the answer is eye. (Adds one letter Y.) If the question is a riddle, the answer is 'envelope' as it begins and ends with 'e', and it contains a letter.
mate ?
strengths
Envelope