enkai - 宴会
This is a drinking party, usually sponsored by an office or place of employment. Japanese people typically don't need much of an excuse to drink, so pretty much any organization will have these with some frequency. Usually they happen at the beginning of the year, the end of the year, when someone new starts or someone leaves, or pretty much any other time that someone can think of any flimsy excuse. Usually these events have a set price and are both tabehodai and nomihodai.

tabehodai - 食べ放題
Tabehodai means all-you-can-eat. It is common to buy an hour or two hours of tabehodai. See also nomihodai, all you can drink, which is a lot more common.

nomihodai - 飲み放題
All-you-can-drink. Very popular among pretty much everyone, because getting smashed is a national pasttime in Japan. Fora few thousand yen you can get an hour or two hours of all you can drink, which includes beer, cocktails, or sake.

ganbatte - 頑張って
A very common phrase in Japanese with no exact correlary in English. Most often used used to say "Good luck!" or "Keep trying!" or "Do your best!" or "Don't give up!" or "Hang in there!" or even "Get well soon!"

keitai - 携帯
A mobile phone. The full name is keitai denwa. It kindof means "wearble" or "sidearm." Obviously everyone in Japan has one of these.

honto - 本当
Means "true" or "truly." Used as an interjection quite frequently, like "Really?"

genki - 元気
Genki is another word that doesn't translate very well into English exactly. It kinda means happy or perky or just fine. Genkiness is having a kindof outgoing personable energy and being friendly and happy. Being genki is very important in publis relations type jobs, such as teaching. Also used as a general greeting along the lines of "How are you?" as in "Genki?" "Hai, genki."

onsen - 温泉
Onsen is a Japanese mineral hot spring spa or bath. Very popular and available pretty much everywhere in Japan, at resorts or vacation spots. They are very relaxing and very very hot. Usually all the girls go to one side and the guys go to the other. everyone is naked with the exception of a small washcloth that you soak in the hot water and put on your head.

omiyage - お土産
Omiyage are little presents that Japanese people give whenever they meet new people or return from a vacation. When you get a new job you should give omiyage to all your coworkers and you bosses. When you move into a new home you should give omiyage to your new neighbors. And when you return from a vacation, you should give something from the place you visited to all your coworkers and friends. Usually these are pretty small things, most commonly sweet foods like a snack cake or something, although this can vary based on the duration of the travel and the importance of the recipient. This is quite a lucrative industry because it is highly unacceptable socially to forget omiyage, and so everywhere in Japan you can find omiyage shops at train stations selling little packages marked from that place in sets of 10 or 20 or 40.

keisatsu - 警察
Police, the cops, the fuzz. In Japan they don't even carry guns and they wear the goofiest colorful uniforms.

ichinensei - 一年生
First year student.

ninnensei - 二年生
Second year student.

sannensei - 三年生
Third year student.

shogakkou - 小学校
Elementary school. Consists of the first six years of schooling, corresponding to first through sixth grade in American schools.

chugakkou - 中学校
Middle school. Consists of three years of schooling, corresponding with seventh through ninth grade in American schools.

koukou - 高校
High school. Consists of three years of schooling, corresponding to tenth through twelfth grades in American schools. Not mandatory in Japan, although everyone goes. Tests to get into a good high school are very rigorous and students spend all of the third year of middle school studying for them and going to juku after school.

juku - 塾
Cram school. Students go in middle school to cram for high school entrance exams.

purikura - プリクラ
Short for Print Club. It's a kind of tiny little photo that's immensely popular among schoolgirls. Usually the photo booths are in game centers, but they can be found in a wide variety of locations. All the best ones are at the game centers, where there is usually a whole floor dedicated solely to them, and crammed end to end with nothing but high school and junior high school girls. For this reason, guys aren't allowed there unless accompanied by a girl. Anyway, there's a booth, into which it is possible to cram as many as eight very friendly people, although usual is probably two to four. First, you put in 400 yen and set some option on the touch screen, and then you get your picture taken in lots of funny poses with wacky backdrops or whatever. Then you go around to the other side of the booth, where you have some time to pick the best ones and draw all over them, adding fruity borders, shooting stars, poo icons, and whatever you feel like writing. A lot of people write the date and location and what they were doing and cute little messages about each other. Then a sheet of tiny little photos pop out of the side of the machine and you cut them up and distribute them among the participants. Typical girls have a book bulging with page after page of these pictures, as well as boxes of extras to give to friends to put in their books.

otaku - おたく
An otaku is a super-obsessed dork. Someone can be an anime otaku or whatever. Americans (especially anime dorks) seem to think that it means "expert" or something along that line, and seem to think that they are cool for using a Japanese word, but are idiots for self-identifying this way because it's definitely a bad thing to call anyone in Japan.