tax, duty
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税 centers on a compulsory payment to authority: a tax or duty levied on goods, income, or transactions.
tax; duty
including tax (of a price); pretax (income or profits); before tax
payment of taxes
taxation
tax increase
customs (duties); duty; tariff
tariff
tax system
customs; customs house
tax office
taxation business
tax reduction
tax evasion
tax counsellor; tax counselor; licensed tax accountant
national tax
National Tax Agency (Japan)
taxes; taxation
tax yields; revenue
tax exemption; duty exemption
taxation law
royalty (on book)
revenue office; taxation bureau
amount of tax
tax collection; taxation
税 combines 禾 (grain) with 兑, which likely contributes the sound and the idea of exchange or payment. Historically, taxes were often paid in grain.
The left side is grain 禾, and the right side 兑 suggests exchange. Picture a farmer handing over a portion of his grain harvest as tax.
For ゼイ, imagine a tax collector saying 'Zay, pay up!' as he takes your grain: Zay -> ゼイ.