I would add that a hobby is just for fun. An interest might be something more serious. My hobby is watercolor painting. (This implies I'm not a professional artist, painting is not my job, etc. Dr Jones has an interest in eradicating malaria and ending world hunger. (These are very serious goals. You would not call them hobbies.)

They are similar, but there is a difference. A hobby usually requires physical objects. For example: sewing, painting, astronomy... An interest can also involve objects or it can be purely in the mind. For example, An interest in philosophy, or science fiction stories, or learning Farsi.

I guess they are similar, but the interest is just that: interested. A hobby is something you actually DO

I agree with the others here hobby is doing something that interests you. Perhaps knitting, painting, or playing chess for fun. an interest does not need to be expressed physically. You can have an interest in politics, vintage cars, or linguistics for example. Interests tend to be purely intellectual. With vintage cars for example, if you collected them, or made models of them, thats a hobby. If you just read about them, that tends to be an interest.

Hobbies-->time you spend doing something Interests-->time you spend doing something The difference is hobbies are typically things that are in the realm of sports, music, crafts that you don't make money doing. Interests are typically more intellectual things you do, or things you do for your career, or things that give your life a deeper meaning. Example: Some of my hobbies are playing guitar, throwing the frisbee, and building model cars. Example: Some of my interest are in history, religious studies, the stock market, and learning Spanish. People will give different answers.