INQUIRE and ENQUIRE are the same word with different spellings. They both mean to seek information or conduct an investigation and are pretty much interchangeable, at least in the United States, but the word inquire (and related words like “inquiry”) are more common everywhere.
In British English, some grammarians make the distinction between inquire and enquire as less formal and more formal. For instance, an enquiry would be a more informal investigation, while an inquiry would be a formal one. The differences are very subtle:
- I enquired the name of the professor.
- The police are going to inquire about the accident.
Whatever you choose to use, make sure you double-check your style guide and also consider your audience. Inquire is always the safest bet if you aren’t sure — and remember to be consistent with your word choice throughout your writing!