Ohayou-gozaimasu - Good morning. Short: Ohayou
Konnichiwa - Good day, hello
Konbanwa - Good evening
Oyasumi-nasai - Good night. Normally used before going to bed. Short: Oyasumi
Sayonara - Goodbye
Arigatou-gozaimasu - Thank you. Short: Arigatou
Sumimasen - Sorry, excuse me
Gomen-nasai - Sorry, excuse me. Short: Gomen
San - Mr/Mrs/Miss, honorific for someone of status equal to yourself. Is to be add at the end of the name
Chan - Honorific for someone of status lower to yourself, and term of endearment for family and friends. Used mostly for females and is very informal. Is to be add at the end of the name
Kun - Mr (junior), master, boy. Similar to chan, but mostly applied to males. Is to be add at the end of the name.
Sama - Honorific for someone of status higher to yourself. Is to be add at the end of the name.
Sensei - Honorific for professors, doctors, teachers.
Hai - Yes.
Iie - No.
Ichi, ni, san, yon (or shi), go, roku, nana (or shichi), hachi, ku (or kyuu), juu - 1, 2, 3, 4, 5.. to 10
Ittekimasu - I'll be back
Itterasshai - Take care
Tadaima - I'm back
Okaerinasai - Welcome back!
Ogenkidesu - fine. Eg, "Sakura-chan wa ogenkidesuka?" "Hai, ogenkidesu"
Gakkou - School
Kaimono - Shopping
Daijoubu - safe, all right, O.K.
Hajimemashite - How do you do?, I am glad to meet you, Nice to meet you
Douzo - Please, kindly, by all means
Yoroshiku - Please remember me, well, properly, suitably, best regards. Eg, "Hajimemashite, Syaoran Bear desu, doozo yoroshiku."
Kawaii - pretty, cute; lovely, charming, dear, darling, pet
Umi - Sea
Ookii - Big
Chiisai - Small
Baka - Stupid. Heard this word in every anime!
Doushite - Why
Ashita - Tomorrow
Asatte - the day after tomorrow
Kyo - Today
Getsuyoobi, Kayoobi, Suiyoobi, Mokuyoobi, Kinyoobi, Doyoobi, Nichiyoobi - Monday, Tuesday... to Sunday
Tomodachi - Friend
Tanjoobi - Birthday
Dare - Who. Word normally used in Sakura's dreams
Koko - Here
Soko - There
Asoko - Overthere
Hayaku - Early, Hurry
Matsu - to wait. Other forms: Chotto mattekudasai - Please wait a little.
Issho - Together
Ikimashou - Let's go
Wakarimashita - I understand. Short: Wakata
Wakarimasen - I don't understand, I have no idea
Shirimasen - inpersonal reply saying "I don't know"
Nandemonai - It's nothing! Meaning easy
Shizumatte kudasei - Please be quiet
Shizuka ni - Be quiet!
Damare - Shut up!
Onegaishimasu - Please. Short: Onegai
Itadakimasu - Said before meals. I am about to partake.
Gochisosama deshita - Said after meals, especially if being treated.
Tomare - Stop

Going to Japan? Read this! Japan FAQ--Japanese Manners and Etiquette