Correct is "co-author," without a hyphen.
Explanation:
- "Co-author" is the correct form in Romanian to describe a person who collaborated on the writing or creation of a work, such as a carte, an article or scientific work, together with one or more other authors. The prefix "co-" indicates collaboration or joint action in this context.
- "Co-author" with a hyphen is not a correct form in Romanian and is not used. Using a hyphen between "co" and "author" would be an orthographic error.
Therefore, it is correct to use "co-author" to refer to a person who collaborates in writing or creating a work with another author or several in Romanian.