On Monday, I forgot to turn off the bath, it overflowed, and our place was flooded.
Please pay the examination fee through your bank by Monday.
On Monday, I would like to watch some fun movies with you, like a steamy romance or blood-curdling horror film. How does that sound?
This is a day of the week. You know this because it has 曜日 in it. But what day of the week is it? The "moon" day of the week is monday. Why? Because "Moon" is pretty much just "Mon," right?
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. It will help to know the word 曜日 as well.