Correct spelling, explanation: the word business has its origin in the word busy to which noun suffix -ness is added. Busy is spelled with y after a consonant at the end so it is changed to i, hence the spelling of business. This also points to the fact that buisness is an incorrect spelling.

Idioms and phrases with business:
→ (not) sb’s business/none of one’s business, (not) something that one should be worried about; (not) something one should know about: Jackie shouldn’t be so interested in this case. It’s none of her business.
→ business is business, used to say in situations when pursuit after money or success is more important than personal feelings: He betrayed us, but he just said “business is business” and left.

Definition of business:
noun, a job or a form of company or deal
John had a well-prospering business, but he decided to sell it and move to the village.
I feel stressed before this next business meeting. It is very important for us.

Incorrect spelling, explanation: this is a wrong form, because the word business is simply a noun created from the adjective busy with suffix -ness. Y at the end is changed to i when the suffix is added, because it stands after a consonant. Therefore spelling buisness is wrong and the correct form is business.

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling

Incorrect spelling