The sport's name:

剣道 ［けんどう］kendo: specifically for the sport.
剣術 ［けんじゅつ］kenjutsu: an older term for fencing, ditto
剣法 kenpo, 撃剣 gekken

The weapons:

竹刀 shinai: (bamboo) fencing stick
木剣 bokken: wooden sword
柄 tsuka: leather hand grip
鍔 tsuba: sword guard, brim (alternate 鐔 )
鍔止め　tsuba dome: stopper ring for tsuba

The strokes:

面 [めん] men: face, face guard
籠手［こて］kote: hand guard
突き [つき] tsuki: a thrust, a lunge
胴 [どう] do: trunk, body, frame

The armor:

防具 bogu: protective gear.
垂れ tare: hanging,　skirts of a coat
袴 hakama: man's skirt
手拭 tenugui: hand towel (head wrap)
鉢巻 hachimaki: headband (alternate term)

Stances:

構え kamae (-gamae): posture, pose, style
上段 jodan: high [of three levels]
中段 chudan: middle kamae / position
下段 gedan: low kamae / position
脇 waki: side kamae / position
八相 hasso. lit., "eight forms / appearances" [of Buddha]
右　-migi: right side, so (右脇) migi-waki: right-side waki
左　-hidari: left side, so (左脇) hidari-waki: left-sidewaki

Positioning principles, movements:

気合い・気合　kiai. yell with "ki" (force?).
空き・隙き suki: opening
間合い・間を取る　maai, ma o toru: spacing
残心 zanshin: alertness
素振り suburi: sliding, gliding (warm-ups).
型　 kata: the ten two-person set forms
打太刀　uchi-dachi: 1st (unsuccesful) kata striker
仕太刀 shi-dachi: 2nd (successful) striker
抜き　-nuki: strike after pulling back, avoiding
返し -kaeshi: return, turn back (a stroke)
切返し　kirikaeshi: a two-partner floor exercise
引き -hiki: strike on pushing away

Practice-related terms:

道場 dojo: hall used for martial arts training

稽古 keiko: practice.
組手kumite: practice fight.
始め！ hajime!: begin
止め！　yame!: stop, quit
試合 shiai: formal contest (of fencing, etc.)
礼！　rei!: bow, give respect
師範 shihan: (an) instructor, (fencing) teacher
蹲踞 sonkyo: formal bow-in of a match
正座 seiza: sit on knees (to meditate / give "rei")
黙想 mokuso: lit., quiet thinking
法界定印 hokkai join: traditional kendo hand gesture used in meditation

Miscellaneous martial arts terms:

居合道 iaido.
合気道　aikido.
柔道 judo.
空手karate.
弓道 kyudo. sport archery.
忍術ninjutsu, ninjitsu.
武道 budo: martial arts
相撲 sumo: wrestling.
太刀 tachi: long sword (katana)
大刀 taito: long sword
脇差 wakizashi: short sword
短刀 tanto: short sword, dagger
杖 jo: long staff
棒 bo: shorter staff
薙刀 naginata: halberd
手裏剣　shuriken throwing blades.
宮本武蔵 Miyamoto Musashi
『五輪書』 Gorinsho: Book of Five Rings, authored by Musashi. exploits to be taken with a grain of salt.
武徳会 Budokukai. First Kendo association, organized first formal tournament in 1896.

Religion and Martial Arts:

不動 Fudo. Shingon Mikkyo god, originally an Indian deity that symbolized one not swayed by external phenomena and hence immoveable. Many samurai worshipped this deity to nurture that mindset or "heart". There are several Fudo [buddhist] temples near Tokyo.
心 kokoro, shin. heart or spirit, as in 「不動心」.
法界定印 hokkai join: hand gesture - mudra - used in kendo, from Shingon Mikkyo Buddhist meditation. the "kiai" correlate with the verbal mantra.

Note that in Christian and Jewish practice prayer also combines physical posture, verbal practice and a quiet attitude. Sport fencing - kendo - developed without a religious orientation, though it adopted various traditional practices. During the 1930s, the Japanese government tried to associate martial arts with the state religion (which formalized folk practice - a syncretic mix of animism and Buddhism - into "Shinto"), including kendo and judo in the school system as good ways to attain a "Japanese spirit." In addition, several popularizers of Zen Buddhism in the West also taught martial arts, and so tried to emphasize that athletics could be approached as a "religious" practice. However, such religious overtones are neither a necessary nor a historic element of kendo as it was developed in the mid- to late-1800s, and were explicitly repudiated when the first post-WWII kendo association was formed in 1952.