The term bokken (kanji: 木剣) means "wooden sword" in English. It is written ぼっけん in hiragana. It's pronounced roughly like "boke-ken".
Literally, wooden sword. 木 is pronounced boku in the Chinese reading and ki in the Japanese. Ki can mean wood or tree. (One can say ki in conversation without the risk for confusion, provided that the context is there.)
剣 is pronounced tsurugiTSURUGI 剣 "sword [non-Japanese]" learn more... in the Japanese reading. Both kenKEN 剣 "sword [non-Japanese]" learn more... and tsurugi mean sword and, similarly, can be used on their own. However, neither ken nor tsurugi is used to refer to Japanese swords.
In Japan, the more commonly used word for these wooden swords is bokuto (木刀, literally wooden katanaKATANA 刀 "sword" learn more...). Bokken and bokuto refer to not only wooden katanas but also wooden wakizashiWAKIZASHI 脇差 or 脇指 "medium-length sword" learn more..., tantoTANTO 短刀 "short sword" learn more..., etc.