Another entry in our series of Japanese terms that are relevant to Berserk. This time, it's all about the Black Swordsman, because Berserk wouldn't be Berserk without him. Black Swordsman is two words in Japanese, like in English. It's written 黒い剣士 and pronounced "KUROI KENSHI".
黒 means black, and adding い to it makes it an adjective. If you'll remember in our previous entry, we mentioned the "White Falcon", and that used the adjective 白い (SHIROI). Same structure.
剣士 (swordsman) is composed of two kanji. The first word is the one for sword (KEN), the second refers to a warrior (samurai) in this context. More generally it can also be used as a suffix to indicate someone has a given profession (SHI). For example, 運転士 (UNTENSHI) means a professional driver, like a train conductor or a bus driver.