Have a nice day!

necessity (quality or state of being necessary, unavoidable, or absolutely requisite)

unnecessary

needlessness

necessary evil

one, 1 / the first in order, foremost / the beginning / the best / a kind of; one of something / (card games) an ace / unity / the bottom string of a shamisen or other Japanese musical instrument

sun / daytime, daylight / day

the daytime, during the day / a half day, half of a day

the eighth day of the month / eight days

the ninth day of the month / nine days