This document discusses the terms "inquire" and "enquire" and their different usages in British and American English. It also discusses letters of enquiry, which are business letters sent to request information about prices, quality, quantity, terms, etc. of goods or services from suppliers. There are two main types of enquiry letters - solicited enquiries in response to advertisements, and unsolicited enquiries without prompting. Enquiry letters should directly state the purpose, requirements, and urgency of the request for information. Various formats and contents of effective enquiry letters are also outlined.