Okay, we have three words that are comepting right now, Kumdoga( 검도가 ), Kumdoja ( 검도자 ), 검도인(Kumdoin). You can type all three Korean words in google and see how many people actually using such words. And these are the result; Kumdoka( 검도가 ): 0 Kumdoja( 검도자 ) : 0 Kumdoin(검도인 ) : countless..... Kumdoin( 검도인 ) is what everyone is using. But mostly we use such word Kumdoin in writing. (Wrong), Are you a Kumdoin ? others will say (what the hell are you talking about?) (Right way of asking) Do you practice Kumdo ?