‘Enquiry’ and ‘inquiry’ mean exactly the same thing… except for when they don’t. And if that sounds confusing, you’re correct. Nevertheless, we’re here to help you avoid errors in your written work. And to do that, we’re going to begin by looking at the traditional definitions of these terms.
Enquiry (A Request for Information)
In Australian English, the noun ‘enquiry’ has traditionally meant ‘a request for information’. It therefore has a very general use similar to the word ‘question’. For example:
All customer enquiries were addressed within 24 hours.
The verb form of this word is ‘enquire’, which means ‘request information’ or ‘ask a question’:
May I enquire about the price of this puppy in the window?
As with ‘enquiry’, the verb form has a very general use and applies to any request for information.
Inquiry (A Formal Investigation)
The traditional meaning of ‘inquiry’ in Australian English is ‘a formal investigation’. For example:
The police inquiry will begin on Tuesday.
The verb form of this term is ‘inquire’ and also applies to formal or official investigations:
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The new study will inquire into rising puppy prices.
These words have therefore traditionally had a more specific meaning than ‘enquiry’ and ‘enquire’.
Modern Usage
The traditional difference above is less common than it used to be. This is because American English uses ‘inquiry’ for both definitions. Consequently, in America, we could say both of the following:
All customer inquiries were addressed within 24 hours. ✓
The police inquiry will begin on Tuesday. ✓
This usage is now common in Australian English, too, although ‘enquiry’ is still used here (and may be considered more correct in formal writing).
Enquiry or Inquiry?
Ultimately, this is a matter of context and preference. In formal writing, it may be better to use ‘inquiry’ only for formal or official investigations, with ‘enquiry’ used more generally.
But in most modern contexts, these terms can be used interchangeably, especially if you are writing for an international audience. Just make sure to be consistent in how you use each spelling!