noun
addressee's name and address; mailing address
Refers to the written name and address of the recipient on a letter or package.
封筒に宛書を書く。
Write the addressee's name and address on the envelope.
宛書が間違っていると、手紙が届かない。
If the mailing address is wrong, the letter won't be delivered.
Compound of 宛て (ate, 'addressed to') + 書き (kaki, 'writing'). The exact historical derivation is uncertain, but the spelling is conventionally associated with addressing mail.