いらっしゃいませ。

Irasshaimase.

Welcome. (shop staff to a customer)

Word for word

“Please come in.”

Politeness: Formal

Honorific or humble language, or a set business phrase. Customer service, email, speeches.

When you would say it

What staff say as you enter a shop or restaurant.

Worth knowing

You do not have to reply. A small nod is enough.