You say this when you want to congratulate someone on a birthday, for winning an award, or on some other happy occasion. You can use just "OMEDETOO" with your close friends; the reply for this would be "ARIGATOO."
"Omedetoo gozaimasu." = Congratulations
"Arigatoo gozaimasu." = Thank you very much.
Note: In the system of romanization used in this section, "ee" is not pronounced like feet. Instead, it means that the vowel sound "e" as in pet is prolonged. In the same manner, "oo" is pronounced not like shoot but as the "o" vowel, similar to pork, pronounced twice as long.