The word coronavirus is the most commonly used term, and it is the only one used oficially by the World Health Organization (WHO). Both coronavirus and corona virus are correct ways to refer to the family of viruses that includes the virus that causes COVID-19. It is important to Both coronavirus and corona virus are correct, but coronavirus is the more commonly used term.

Correct spelling, explanation: not recommended, less popular version. Corona virus is a less common way to refer to these viruses, and it is not used as frequently in the scientific or medical literature. It is formed by combining the words corona and virus separately, rather than using the combined form coronavirus.

Correct spelling, explanation: recommended, more prevalent spelling. Coronavirus is a combination of the words corona, which refers to the crown-like shape of the virus when viewed under a microscope, and virus. The word corona is derived from the Latin word corōna, which means crown or wreath.

Sentence examples with coronavirus/corona virus:
The best way to protect yourself from the corona virus is to wash your hands frequently and avoid close contact with sick individuals.
The World Health Organization has declared the coronavirus outbreak a global pandemic.
Symptoms of the coronavirus include fever, cough, and difficulty breathing.