In my taekwondo class the instructors tend to pronounce the Sino-Korean version of the number 2 as Yi or "yee" - as opposed to "ee" (이). Is this correct and, if so, how is this written in Hangul?
--- Thanks!
Koreans have the syllable "이" which is pronounced like saying the letter "e".
However the romanization of this is quite a challenge. We've seen (in names)
Lee, Yi, Ree, Rhee (and etc).
My guess is that the instructors saw the sino-korean numbers romanized and are thusly pronouncing it as seen in romanized sino-korean "Yi"; however, this is not the correct pronunciation. See the youtube video on English Long E sound /i/ because it is nearly identical.
And as you stated in the question, the correct hangul for the sino-korean number two is
이