Something you enjoy doing on a constant and semi regular basis in your free time. So it's essential you have free time, and something you enjoy.
It helps keep your mind healthy by doing something other that you have to, such as paid work.
It creates a sense of achievement and well being, which is sometimes lacking in a paid job.
It's a form of self imposed, occupational therapy, saving the devil making work for idle hands.
Staying active a necessity for someone in their retirement years. Maintaining a hobby, joining a senior's group or volunteering will go a long way to combat the isolation and depression that often accompany retirement.
No, it's not a necessity like tractors and harvesters are. But there are some farmers that like to have an airplane as a side-hobby so they can just get away from it all and go for a flight around the countryside.
The possessive form of the noun necessity is necessity's.
The plural of necessity is necessities.
Twitter is not a necessity.
necessity
necessity
No, more people watch Football every year than go fishing. Fishing is a hobby while watching football is considered a necessity for some men out there.
Necessity.
necessity
The word "hobby" like a hobby you have, for example "collecting sea glass is my hobby", the word hobby is a noun. Though in the phrase 'hobby horse' it serves as an adjective.
She collected bugs as a hobby. Her hobby was sewing.