How to differentiate kanji compounds from regular kanji


For example, how do I know when 日本 is talking about Japan and when it's
talking about a book about the sun. I'm very early into learning kanji so I
apologize if this is a dumb question.




日本 is always taken as **one word** meaning "Japan". It does not mean "a book
about the sun", even though the kanji 日 and 本 in isolation have the meaning of
"sun" and "book", respectively.

In Japanese, you have to use something called **particles** to express longer
concepts like "a book about the sun". Particles are small function words that
roughly correspond to English prepositions (e.g., "to", "in", "from", "about",
"by"). In English, "bookend" and "the end of a book" refer to clearly
different things, right? Likewise, since there is no particles between 日 and
本, 日本 will be taken as one word. (This is a basic rule. As you continue
learning Japanese, you will encounter many tricky cases where two words are
connected without particles. For details, see [How to separate words in a
Japanese sentence?](https://japanese.stackexchange.com/q/11687/5010))

FWIW, "the book about the sun" is 太陽についての本 in Japanese. 太陽 is a word meaning
"the Sun", 本 is "book", and についての corresponds to "about".

