A check may refer to any of the following:
1. A check is a single step that is performed to verify something is working. For example, a user may check their power cable to make sure it is connected to the computer if they cannot turn on the computer.
2. A check or check mark ( ✓ ) is a symbol used to indicate something is selected as shown in the picture. See our check box page for an interactive example of check marks placed in a check box.
Should I use "checkmark" or "check mark" in my writing?
Both forms are correct, and its usage depends on the style guide you're following. When describing a symbol, we follow the Microsoft Manual of Style and write "check mark" as two words in all of our writing.