The term "purchase" is a verb meaning to buy, or a noun meaning an item obtained through a sale. However, the word has been used in many major historical terms, including:
The word purchase is often used in contracts with "acquisition", as in the term "Acquisitions and Mergers" (A&M) in legal agreements made between large companies. Those contracts typically state than a company was purchased by another company.
In common usage, the shorter word "buy" is typically used when shopping, rather than the word "purchase". In legal terms (legal words), the opposite of a purchase is called a "sale".