Most common Japanese for “good morning” is “ohayou”.

You can say ohayou to family members, friends or your colleagues.But you should not say “ohayou” to your boss or audience (at the beginning of your speech).


Because ohayou is not very polite. So to your boss,audience,or people you do not know, “ohayou-gozaimasu” sounds better.
 
ohayou-gozaimasu(おはようございます)
=good morning sir (or ma’am) (to your boss, customer, or audience)
 
ohayou(おはよう)
=good morning ( to your family members, friends, or colleagues)
 
In Japan, at a workplace, ohayou-gozaimasu is sometimes used to your colleagues.
 
 
ohayou(gozaimasu) is used in morning time, so maybe until 10 o’clock in the morning, We use ohayou(gozaimasu). After 10 o’clock, konnichiwa(こんにちは) is appropriate.
 
konnichiwa(こんにちは) is used until around 5 o’clock, then we say konbanwa(こんばんは) in greetings, which means”good evening.”
 
 
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