[Frank focuses on his commander's words, repeating them to memorize it. It is pretty confusing.]

'E'. Pronounced as 'Ee', 'eh' or 'ee'. 'Elation', 'excited'... Occasionally silent... Similar sounding to two other letters... Can denote a long vowel...

'Endurance', 'espionage'... Those are 'eh' sounds. 'Elisa', that's 'ee'...