Correct spelling, explanation: the origin of the word vision can be found in videre, which was a Latin word for to see. Later the word also entered Old French and then in the times of the Middle Ages vision appeared in English, too. Back then, however, vision referred to some supernatural or religious experiences.

Definition of vision:
1. noun – a mental idea of something,
The latest novel by this author shows an apocalyptic vision of the future, which makes you feel really uncomfortable.
2. noun – the ability to see with the use of your eyes,
Because of the heavy rain, I had poor vision of the road.
3. noun – something that you see in your dreams as a result of some supernatural or religious experience,
Due to her mental illness, she had visions in which God was speaking to her.

Expressions with vision:
Some popular expressions with vision are: vision loss, night vision, and 20/20 vision.
The accident was so serious that it resulted in vision loss for the boy.
I hate driving a car at night as my night vision is really poor.
It’s amazing that at the age of eighty he still has 20/20 vision.

Incorrect spelling, explanation: the pronunciation of the word vision suggests that there is no -i letter in the second syllable of the word. As a result, a popular mistake is to spell vision as vison, which is wrong as the second syllable also needs to feature the -i letter.