Noun, する verb, and の adjective
しんだん
私の息子は四歳の時に喘息だと診断されました。
My son was diagnosed with asthma when he was four.
I'm going to cut off the part of me that I'm trying to diagnose... well, not literally cut off, but cut off my diagnosing. I have come to a conclusion. A diagnosis!
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.