Key Difference: A minor refers to somebody who is not yet an adult, at least not in the eyes of the law. The person can be a child or a teenager, as long as they can’t be called as adult. Juvenile may indicate or reference legality. While it does technically mean young, the term is often also used in the sense of the law, where it refers to a young person who has been accused of a crime.

Both minor and juvenile refer to young people, usually below the legal age, which in most countries is 18 years of age, and in some countries is 21. In technicality, both the terms have similar terminology and there are instances where the terms can be used interchangeably. However, in practicality each of the two terms has difference implications and hence are colloquially used differently from each other.

A minor refers to somebody who is not yet an adult, at least not in the eyes of the law. The person can be a child or a teenager, as long as they can’t be called as adult. Hence, in this context minor is the opposite of an adult. Yet the term is also often used to refer to something that is less important, serious, or significant; e.g., minor inconveniences or minor disruptions.      

The term is also commonly used in music or sports. In music the term refers to the type of scale, key or mode; e.g. the song in E minor, or the minor chord. In terms of sports, the term is often used to refer to the minor leagues. The term may often also be used to refer to the focus of study, e.g. a minor in psychology.

Juvenile, on the other hand, may indicate or reference legality. While it does technically mean young, it has a negative connotation to it. It tends to imply immaturity and childishness, rather than refer just to the age. In addition, the term is often also used in the sense of the law, where it refers to a young person who has been accused of a crime. In this context, juvenile is sort of the opposite of a minor. Minor indicates an innocent child, whereas juvenile tends to imply a young criminal.  

So, in summary, the terms ‘minor’ and ‘juvenile’ mean the same thing, however they have different implications and contexts to each of them. Minor implies young and naïve, whereas juvenile indicates either immaturity or a young criminal. However, one must be careful while using juvenile because they may call someone juvenile, i.e. indicating that they are immature, but might insult them if the person thinks they are being called a criminal. So to be on the safer side, outside of the context of law, better to use minor or just use common terms such as naïve or immature.

Comparison between Minor and Juvenile:

Reference: Oxforddictionaries.com (Minor and Juvenile)
Images: newsnish.com, peteearley.com