Fact, Reality
Noun
じじつ
事実かもしれないけど、なっとくはできないな。
That may be true, but I'm still not convinced.
あのせいじ家の言っていることは、事実に反します。
What that politician has been saying contradicts the facts.
口髭を生やした男が気味悪く見えるのは、科学的な事実です。
It is a scientific fact that a man with a mustache looks creepy.
The action of truth is just truth itself, though it's also facts and reality as well. Really, it's the idea of "truth" in a way.
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.