打招呼 (dǎ zhāo hu): 言葉や行動で挨拶する；事前に通知する

He greets his neighbors every day.

When you meet a friend on the street, greet them warmly.

When meeting for the first time, we should greet politely.

He is used to greeting people with a smile.

If you leave without saying goodbye, it will seem impolite.

He greets his neighbors every morning.

You need to notify the company about this matter first.

When they met, they just nodded without greeting each other.