There are a lot of words in WK that have the definition “reality”. I felt like I was getting them all confused, so I drew from the context sentences provided by WK and tried my best to boil them down here. Let me know if there’s anything that needs to be corrected, I wasn’t able to figure out how to distinguish all of them.
- 事実 - Noun – Truth or fact. 科学的な事実 is “scientific fact”
- 実在 - Noun – “real existence”. Something that really exists. 実在の人 is a “real, nonfictional person”.
- 現実 - Noun – Reality itself. This is reality in the pure, abstract sense.
- 本当 - Can be in adverb form as 本当に. Very common, used to say whether or not something is really true.
- 真実 - A noun, but can be used as an adverb or adjective. Can’t really figure out the nuance on this one. 真実の愛 is “true love”, but also you can say 真実ですか to ask if something is true? You can also say 真実から目を背けないで to literally say “don’t turn your eyes away from the truth”. EDIT: As @Leebo says, this is the truth you search for in a mystery.
- 実 - noun, の adjective. 実は is a way of saying “well actually,” or “truth is,”. 実のところ is a fixed expression that says “as a matter of fact, I…”, or “to tell the truth, I…”
Man, that’s a lot to dig into, but typing this out actually helped me a bit.