What does the word hello in Japanese mean?

konnichi WA
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It kind of depends on the time of day.

Up until about 10 in the morning, you would say Ohayo gozaimasu (Sounds like "Ohio Go Zai mus" which means "Good morning (politely)

After about 10 a.m. until it starts to get dark, you would say konnichiwa (Ko nee chee wah)

In the evening, it would be kombowa (kohm bow WA).