Translation:the Klingon vowel e
Remember to put the apostrophe at the start. It is a full letter of the alphabet and is called a qaghwI'. The "sound" it makes is called a glottal stop and it's really a stopping of sound rather than a making of sound. In English, when we say words that start with vowels we usually start with the glottis closed, so we actually make a lot of glottal stops, but we don't mark them in any way, so we don't even consciously realize it. So to an English speaking ear, we don't hear anything before they e in 'et, when really we do make a glottal stop. In Klingon you have to mark that with a qaghwI'. No Klingon word starts with a vowel, even though it can sound like it to English speakers.
I know where it comes from.
As 'et means fore, Duj 'et means bow and in some contexts 'et would be sufficient to mean bow.
As 'et means the vowel e, it would be easy for a student to extract simply vowel from that.
The exercise accepts various forms of e and the vowel e plus fore but not bow.