Restroom
Bathroom, Toilet
noun
*Ahem.* This is the convenience facility. What place above all others should be convenient to get to? You know, just in case? That would be the restroom. You might also call it the bathroom, the toilet, the lavatory, or the facilities.
This word is casual and can often sound gruff, so you won't normally see it on official signs or hear it in polite conversation. It's worth knowing so you can understand it in casual speaking and writing though.
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. Just watch out for the rendaku.
便所のドア
toilet door
便所の出入り口
bathroom entrance
便所のにおい
toilet smell
やばい。便所サンダルで学校に来ちゃった！
Oh snap. I came to school in toilet sandals!
ちょっとコンビニの便所行ってくるわ。
I'm going to a convenience store bathroom real quick.
「便所」っていう言葉はちょっと下品ですよ。
The word 便所 sounds a bit vulgar.