In japan people greet each other based on the relationship. But there are some greeting which are without any relationship and are dependent on situations. Take case of saying, good morning for example. You can say good morning to any person before clock hits time 12 am. This is quite natural in every part of the world. In japan some people say good morning only upto 9am and after that regular greet of ‘good day’ follows. Still there are some folks who follow 12am as pointer to say good morning.
Good morning in Japanese is written as – Ohayou gozaimasu
おはようございます。
In some cases gosaimasu is dropped and people around you will say ohayoo only. Here ohayoo means morning, which is casual usage. This is also acceptable among friends and family but it’s usually not preferred when you’re greeting seniors in house or office. So take care of this note while greeting any senior around you in japan.