Quick question about Kanji pronunciation.
 

Hello all, I have recently been learning Kanji from this book:
Amazon.com: Basic Kanji Book, Vol. 1: Chieko Kano, Hiroko Takenaka, Eriko Ishii, Yuri Shimizu: Books

I have a question about the Kanji readings. For example, you have 日, and the kunyomi reading is ひ while the onyomi reading is ニチ. How do I know which one to use? I get confused about this because in the book it has:

門, with the kunyomi reading as　かど and the onyomi reading as モン. In the two examples it gives me, it has this:

門（もん） a gate
専門（せん・もん） a specialty

In both of those cases, it is using the onyomi reading. Any help will be appreciated. Thanks! :D

I am not sure how to know which one to use.

As a rule of a thumb:
- it is onyomi when it is a single or a pair of kanji, or a cluster of kanji.
- it is kunyomi when the kanji is follow by a/some hiragana.

Don't worry, once you have advanced yourself further, you'll know how to differenciate between the two. Don't rush yourself.

Ah, now that I think back on that, it makes sense. Thank you a lot for the response.

Except if it someone's name, of course....

.......and the exception also applies to if it is a name of a place.

Thank you very much for sharing.
Look forward to your another article.