noun
registered mail fee
The postal charge added when sending a letter or parcel by registered mail (書留).
書留料は普通郵便の料金に加算されます。
The registered mail fee is added on top of the regular postage.
書留 refers to registered mail itself, while 書留料 is specifically the fee for that service.
Compound of 書留 (registered mail) and 料 (fee).