Learning Kendo does not require fluency in Japanese, however, there are a few things you should be able to say and understand in the Japanese language. If you are studying any traditional martial art, from any culture, you should master the basics of related vocabulary...

Be able to count from one to ten in Japanese:
One - ichi (pronounced "eechee" - but a little short on the "ee")
Two - ni (pronounced as in "knee")
Three - san (close to "son")
Four - shi (pronounced "she")
Five - go (sounds kind of like it's spelled, except with a Japanese accent)
Six - roku (actually, there's no R sound in Japanese - sort of roll an L and you've got it)
Seven - shichi (see ichi)
Eight - hachi
Nine - ku (as in "kudos")
Ten - jyu (same "u" pronounciation as in "kudos")

When starting to play with a new opponent, you should start with the following phrase:
"Onegai shimasu" (general translation: "Please let me train with you")

When you finish playing an opponent, you should thank them:

"Arigato gozaimashita" (when bowing to a sensei, you should add "Domo" at the start to show respect)

Other Kendo terms in alphabetical order:

AITE: Rival, competitor, opponent or adversary.
AIUCHI: Action of two opponents in which both score a point in combat, simultaneously.

BOGU: Armor used in Kendo, consistent of several protectors: Men (head and face), Kote (forearms and hands), Tare (hips and stomach) and Do (breast and ribs). Also known as Dogu.
BOKKEN: See Bokuto.
BOKUTO: Sword made from very hard wood, usually 1.05-m length, with the real shape of a Katana. Its use is identical to that one of a metal sword. History tells that Miyamoto Musashi killed his personal enemy Sasaki using a Bokuto made out of a branch. Also known as Bokken.
BUDO: Literally " the way of the combat ", this term was adopted in the 20th Century to applied to Martial Arts in general, emphasizing its pacific aspects. In addition to the physical discipline and the different techniques, it implies an attitude of mind, spirit and of certain ethics. The Budo term differs from the Bujutsu, in which the latter is related more to real battle, whereas Budo emphasizes not only the physical development, but also the mental control and spiritual depth.
BUSHI: "Warrior". This was the name given to the ancient Japanese soldiers from traditional warrior families. The Bushi class was developed mainly in the north of Japan. They formed powerful clans, which in the 12th Century were against the noble families who were grouping themselves to support the imperial family who lived in Kyoto. (See Samurai).

CHIKA-MA: See Ma-ai.
CHUDAN: " Mid-level ", at the level of the chest. Chudan-no-Kamae: usual guard position, with the end of the Shinai directed towards the throat of the opponent.

DAISHO: Pair of swords used by the Samurai and Bushi of high rank. It consisted of a Katana (or O-dachi) and a Wakizashi (or Ko-dachi).
DAN: Expert's degree. The most basic is the Shodan (first), which is immediately superior to the 1st Kyu. In Kendo there is a maximum of 10 Dan.
DO: Protective piece destined to cover the chest and stomach. Hard and rigid, it was originally made out of lacquered bamboo, although modern ones are also made using synthetic materials.
DOGU: See Bogu.

GEDAN: "Low-level". Gedan no-Kamae: low guard, with the Shinai to the front and the tip directed downwards.
GOKAKU GEIKO: Training between students who have similar force and are more or less at the same level.
GYAKU DO: The left part of the Do. It is a cut not used much in combat, but can be very effective to the one who is able to master it.

HAJIME: Command that is told by the instructor at the beginning of an exercise or fight.
HAKAMA: Skirt-like pants which are still worn in traditional ceremonial customs in Japan. The Hakama has two folds in the rear, and five on the front, each one with its own meaning.
HANSHI: "Masterful". Honorary title given to the teachers of higher degree, meaning their appropriation and understanding (Kokoro) of the art.
HARA: The internal center of gravity of the human body, usually located four centimeters below the navel, between this one and the spine. According to the Japanese belief, it is here where vital forces reside, and it is also from this point where deep breathing must be originated.
HASSO: Hasso no-Kamae: position in which the Shinai is maintained vertically with the hands to level of the shoulder of the right or left side.
HATSU-GEIKO: New Year's training, which lasts several days and finishes with competitions and special events.
HIDARI: Left (i.e.: Hidari Do: Left part of the Do).
HIKI: To evade. Hiki-Age: Action to raise the Shinai high after making a cut, preparing oneself to do another one downwards. Hiki-Waza: Backwards movement techniques. They are carried out when one is in Tsuba-Zeriai or another close position in which the opponent can be caught without consistent guard.
HIMO: Literally meaning "cord ". It is used in Kendo to tie the different parts of the Bogu (protective equipment).
IAIDO: The art of drawing a sword out of its scabbard, as fast and clean as possible, with evident naturalness and fluidity, being the main objective to cut the enemy long before he is able to draw his own sword or use any other type of weapon. The great masters of this art have gotten to be able to draw the sword and sheathe it back again with the speed of a lightning. Iaido is a sister art to Kendo, and is recommended when having certain experience in the latter. Iaido is also internationally regulated by the International Kendo Federation (IKF).
IPPON SHOBU: A one-point combat.
ISSOKU-ITTO-NO-MAAI: "One step, one blow" See Maai.
ITTO-RYU: (ITTO= 'one' sword; RYU= school). School created by Itto Ittosai, who used a single sword with both hands. This style had a great influence in the development of Kendo.

JI-GEIKO: Free style combat, used for training Kendo. More than having a competitive character, it seeks to give the students an opportunity to apply the different techniques that they have learned.
JUTSU: Technique based in the traditions and teachings of a school. A technique can be acquired only after years of training and study.

KACHI: Victory (used usually at Shiai - competitions).
KACHINUKI: Very special training, carried out as a combat, in which a Kendoka takes one opponent after another, successively and without any time to rest, until getting to physical and/or mental exhaustion and suffer defeat. The final winner is the one who has obtained most victories.
KAKARI-GEIKO: Basic attack techniques studied as part of essential training. During Kakari Geiko, the student puts into practice every technique and movement he or she has learned, usually during a short period of time but without pauses between attacks.
KAKEDAMESHI: A strong attack.
KAMAE: Guard or posture. The three basic Kamae in Kendo are the following: Jodan (high), Chuudan (mid) y Gedan (low).
KATA: Kendo forms or sequences, which involve an Uchitachi (the one who attacks - the pupil) and a Shitachi (who counterattacks- the teacher). Kendo Kata are 7 using a Dachi (long sword) and 3 with a Kodachi (short sword).
KATANA: A slightly curved sword, with its convex edge sharpened, used since the Ashikaga period (1333-1474). It was one of the weapons used by the Bushi class, especially the Samurai, which used it together with a shorter sword called Wakizashi. The Katana has been endowed with a sacred element, since it comes from the work store of a member of the Shintoist priesthood. The two swords together are called Daisho (long and short), and were used by Samurai of all the ranks.
KATATE-WAZA: Technique using the Shinai with one hand. It requires great strength in the wrist.
KATSUGI: Shoulder movement that allows giving a blow with the Shinai or shunting an attack.
KEIKO: Training designed to perfect oneself in the art and technique of Kendo, exceeding (Kei) what has been achieved before (Ko).
KEN: "Sword". Name given to the ancient straight and double-edged swords.
KENDOKA: Although it literally means "an expert in Kendo" it is usually applied to everyone training Kendo. Kenshi is used as a more correct term.
KENDOGI: Training jacket, made out from thick cotton, used under the protective armor (Bogu).
KENJUTSU: "The Art of the Sword". The art of using the sword after it has been unsheathed in order to be able to attack the enemy. Iaido is included among the Kenjutsu techniques. It was the warrior art par excellence, practiced especially by the Samurai. Kenjutsu gave origin to the art of Kendo.
KI: One of the most complicated and important concepts of the Japanese philosophy. It concerns directly the daily life, being not less than the vital energy of that life.
KIAI: A kind of explosive sound, some type of controlled and customized shout that seeks to inspire courage and determination in the one who emits it and to frighten the opponent, interrupting at the same time the concentration of the latter. It is originated in the center of gravity of the body, located approximately two centimeters below the navel. It makes use of the KI, or " vital force ", the equivalent of the Chinese CHI (Qi).
KIHON: Basic Kendo movements and techniques. Kihon is repeated until the movement becomes almost instinctive, obtaining a perfect action.
KIKENTAI NO ICHI: Literally it means "soul, sword and body are one". It represents the inseparable nature of these three elements in Kendo. If these are not combined, a blow in a combat cannot be delivered correctly.
KIRIKAESHI: A warming-up exercise in which the students carry out cuts with the Shinai, one after another and without stopping, lifting the Shinai over the head before each blow. Kirikaeshi must be executed until physical or mental exhaustion.
KODACHI: Short sword, also know as Wakizashi. See Wakizashi, Katana, and Daisho.
KOTE: Forearm. Special gloves that cover this part of the body, including the hands. Point that is scored in this part.
KYU: Apprentice's degree.

MA: Global concept that comprises time, space and an interval between two things or two moments.
MA-AI: It means the distance / time that separates two things. In Kendo, it means the precise distance to carry out a movement or technique. There are three basic distances in Kendo: Chika-ma - short distance; To-ma - long distance; and Issoku-Itto-No-Maai - between these two. The latter means, literally, "distance of one step - one blow".
MAE: In front, forward.
MAKE: Defeat.
MEN: Protective mask with metal rods for the face, which also covers the head. Three basic blows to the Men exist: Hidari Men (left), Migi Men (right) and Sho Men (to the center).
MIGI: Right (i.e.: Migi Men: Right Men).
MOKUSO: Moment of silence and meditation that is made generally when starting and finishing Kendo training. It seeks to free the mind, calm the spirit and prepare the student for training.
MUDANSHA: "Without a Dan". Term that is used to refer to the students who have a Kyu, that is to say, that still do not have a Dan.
MUSOKEN: Attacking or defensive movement, completely spontaneous and without the intervention of the thought, anticipating the actions of the opponent. The Musoken represents a type of sixth sense.

NAKAYUI: Small leather cord that limits the superior third of the Shinai, and that in addition keeps the four bamboo rods together.
NAKAYUWAI: Distal part of the Shinai, with which all contact must be done during a blow. A cut will not be correct if it is not delivered with this part of the Shinai. This area is limited downwards by the Nakayui.
NIHON KATANA: Two-sword technique. It is used generally a Katana in the right hand and a Wakizashi in the left. This style was introduced by Miyamoto Musashi. Also called Nito, or Nito Ryu.
NITO (RYU): See Nihon Katana. The Nito Ryu is a style of Kendo, using two Shinai in a combat, although it is rarely practiced nowadays.
NAYASHI: Technique in Kendo with which the Shinai of the opponent is lowered to the floor, after which a thrust to the throat is made (tsuki).
NUKI: Evasion. Nuki-Waza: Evasion techniques. They include a step backwards or a turn made to evade the attack, which causes it to miss, hitting nothing but air. Taking advantage of the sudden loss of balance of the enemy, one can effectively counterattack.

ODACHI: Large sword. See Katana.
OTOSHI: Action of hitting or pushing downwards the opponent's Shinai, generally with a quick but powerful blow of one's own Shinai.

REI: "Respect, veneration". Part of each Dojo's etiquette, it consists of a bow (with the inclination of the superior part of the body) to the opponent, before and after each training. It can be done standing or during Seiza.
RYU: School or style. I.e..: Nito Ryu.

SAKIGAWA: Small leather piece that covers the end of the Shinai.
SAMURAI: A type of warriors (see Bushi), united to a lord in the Imperial Court. The Samurai were there for the protection of their lords, and they were highly trained in the martial arts. The Samurai were the only ones who were allowed carry two swords with them (Daisho). The ethical and moral code of the Samurai has been transmitted through the roots of Kendo.
SANBON SHOBU: The base of Kendo competitions, it means "three-points combat ". Many tournaments now run on an "ippon-shobu" basis, meaning one point against you and you lose the match.
SAYA: Scabbard or case of a sword.
SEIZA: Position taken during rest or while waiting orders, before or during training. One sits on his heels, with the dorsal part of the feet in contact with the ground, just like the knees. Facing the front, the person's back is completely straight, like "a smoke column that rises on a calm day", looking always to the front.
SEME: Threatening attitude, adopted just before lifting the Shinai to make a cut. Seme implies showing spiritual force to the opponent.
SEN SEN NO SEN: Win by anticipating the opponent's intention.
SHIAI: Competition between two or more opponents.
SHIKARE WAZA: Technique in which the Kenshi takes advantage of the low guard of his opponent.
SHINAI: Sword traditionally made from bamboo, which is used in Kendo training. It consists of four rods put together in a careful design that provides damping for each blow. There are many sizes and weights, according to the Kenshi's age and stature. Recently, synthetic Shinai have been introduced, made from carbon graphite.
SHINPAN: Judge or referee in a match.
SHITACHI: When Kata is made, this is the name given to the one who counterattacks.
SHOBU: It previously meant a death match between two martial artists. Nowadays, in Kendo, it represents a match or competition. Shobu Hajime (Hajime!): Judge's words for initiating the match. Shobu Ari: Judge's words announcing a victory.
SHOMEN: A direct blow to the center of the head using the Shinai. Also referred to as Men.
SONKYO: Position that is taken in Kendo before and after a combat or training between two people. The legs are bent, the heels are close to one another, whereas the back stays completely straight. The chin is in a horizontal position, with the look towards the eyes of the opponent. The Shinai is taken exactly in the same way as it is done when the person is standing, aiming towards the throat of the opponent, always ready for a counterattack.
SUBURI: Exercises with the Shinai or sword, which consist of a repetition of the basic cuts. A lot of emphasis is made in these exercises, one has to perform thousands of Suburi before reaching perfection in the different techniques.
SURIAGE WAZA: Technique in which the opponent's Shinai is lifted with one's own, managing to obtain an opening and deliver an attack. Lifting the Shinai and attacking are part of the same movement.

TENEGUI: Small piece of light cotton that is put in the head, similar to a turban, under the Men.
TO-MA: See Ma-ai.
TSUBA: A Shinai's guard; the part of a Shinai that protects the hands..
TSUBA-ZERIAI: Term used to describe a situation in which the competitors are so close one another that the Tsuba of their Shinai is in contact. (See Tsuba).
TSUKA: "Handle" of a Shinai or sword.
TSUKA GAWA: Tsuka Gawa is the leather piece that covers the handle of the Shinai.
TSUKI: Name given to the direct thrust to the throat, using the tip of the Shinai. Tsuki is a relatively dangerous technique in a real match, so that it is only used by advanced students.

UCHI: Word meaning "blow"; [Men Uchi], for example, means "a blow to the Men"; [Kote Uchi] "a blow to the Kote", etc.
UCHIDACHI: When Kata is made, this is the name given to the one who attacks and initiates the sequence of movements.

WAKIGAMAE: A type of lateral guard, with the Shinai in a horizontal position, aiming to give a blow with the tip.
WAKIZASHI: Short sword, a Katana's "companion". Known also as Kodachi. See Katana, Daisho.

YAME: Command used to finish and exercise or a match.
YOKO: Side / lateral. I.e.: Yoko Men: cut given to the side of the head.
YUKEN: Situation in which the swords of two opponents are crossed.
ZEKKEN: The "name pouch" or "tare marker" that identifies the kendoka by club and surname.

ZENKUTSU DACHI: Position with the weight of the body towards ahead and resting mainly on the leader leg (in this case, the one that is more ahead), with the back leg extended backwards.