Ninth Day, Nine Days, Day Nine
noun
Ninth day or day nine. No matter how you look at this word, it makes a lot of sense.
ここのか
Words that count days use an exceptional reading. Even though this is a jukugo word, it uses kun'yomi readings for both of the kanji. You learned this reading for 九 when you learned 九つ, so you should be able to read this one too!
三月九日に、あの女の子は五才になる。
On March 9th, that girl turns five years old.
九日もシャワーをあびてない。
I haven't showered in nine days.
レッスン九日でマリオカートのマスターになれました。ありがとう。
I became a Mario Kart master on lesson day nine. Thank you.