day / sun

daytimes / number of days

the sun / sunlight, sunshine / daytime, daylight / a day / time and date / a daily (something done everyday) / the weather / a (usually unfortunate) case, event, situation

sun / day

Short for 日曜日 (nichiyōbi): Sunday

ordinal day of a month / number of days

one for all, all for one

(poetic, rare) a return letter, a written reply

(poetic, rare) to send a return letter, to reply in writing

(literary) return; repayment / (literary, by extension) reply letter / (literary, by extension) messenger sending such a letter