Coworker-Co-Worker | Commonly Confused Words

Coworker

/'kəʊˌwɜ:kə/

A person who works at the same place as another person

/ˈkoʊ wɜːrkər/

A person who works at the same place as you, typically having similar roles or duties.

Coworker is the standard and widely accepted spelling of the word without a space.
Both coworker and co worker essentially mean the same thing, referring to someone you work with.
In American English, coworker is the preferred spelling.
Some may use co worker to emphasize the meaning by visually separating the prefix from the root word.
Remember that coworker as a single word is more common in most writing contexts.