Hot Springs
Onsen
A warm spring (like the water kind of spring) is a hot spring. These are really nice. You should go to them in Japan.
おんせん
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.
この温泉は、タトゥーのある人も入よくできます。
This onsen is open for people with tattoos too.
かるく運動してあせを流した後、温泉に入ろう。
Let's go to hot spring after sweating a little bit from some light exercise.
私の父も母も温泉が好きじゃありません。
Neither my dad nor mom likes hot springs.