Sad
い adjective
This is a single kanji with しい on the end, so you know it's an adjective. What's the adjective form of sad? It's sad, sadly.
You learned this reading with 悲しむ, hooray!
それは悲しすぎるね。
That's too sad.
悲しいけど、今ので運を使い切ってしまった気がする。
Sadly, I feel like I've just used up all my luck for it.
桃ちゃんが悲しい気持ちの時は、お父さんもお母さんも辛い気持ちになってしまうのよ。
When you feel sad, Momo, neither your dad nor myself are happy.