Nature, Natural
noun, な adjective
Self nature is nature itself. That is nature, like all those green things and 青葉 outside. Many apologies if someone hundreds of years from now is reading this. It used to be pretty green outside before the robots. If you call this "natural" then you are using the な adjective 自然な, but I thought it pertinent to add that in here too.
しぜん
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. Wait! Except 自 is し and not じ! That is because when you add the little dakuten you are adding to the し. When it has no dakuten, it is in the form that nature intended.
日本の自然が大好きです。
I love the nature of Japan.
そう感じてしまうのは、自然なことですよ。
It's natural to feel that way.
ユーザーから、ワニカニを自然に返すように言われました。
We were told by the user to release WaniKani into the wild.