Admission, Entrance, Introduction, Apprenticeship
noun, verbal noun, の adjective
If you are able to enter the gate then you have gained admission and entrance to the facility. Sometimes you do this to start an apprenticeship, where you get an introduction to some sweet new skills, like how to make an entrance.
にゅうもん
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.
まずは入門コースから始めましょう。
Let's start with the introductory course first.
彼は有名なヨガの先生のところに入門したそうですよ。
I heard he started his training under a famous yoga instructor.
この本はプログラミングの入門書です。
This book is an introductory text on programming.