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guest; visitor
customer; client; shopper; spectator; audience; tourist; sightseer; passenger
counter for containers used to entertain guests
「客」 has other readings with different meanings.
今日は客が多くて忙しい。
There are many guests today, so it's busy.
この店は客が多いですね。
This store has a lot of customers.
会社に来た大切な客にお茶を出しました。
I served tea to the guest.