Calling someone a minor can be seen as offensive, or just plain rude. It can make you seem like a jerk or a douche if you're calling someone a "minor" if your conversation has nothing to do with the law. In a way, it could be verybelittling to them.
Minority - smaller number. Like, a religion.
Minor - a key or note. There are major and minor versions of a song.
First example, legal: "you were caught selling alcohol to a minor."
Douchy example: "bruh. You're a minor."
In most countries, any person(s) who is under the age of 18 years. (See example one.)
Less important or urgent (in comparison to other situations or events); has less priority than something else, or something that is not too difficult to solve or clear. (See example two.)