Purchasing is the buying of goods or services. An item that has been bought is called a purchase. The opposite of a purchase is a sale. In common usage, the shorter word "buy" is typically used when shopping, rather than the word "purchase".

However, the word has been used in many major historical terms, including:

• the Louisiana Purchase (of 1803), which greatly increased the size of the U.S.;
• the Purchase System in the British Army;
• the Ashbourne Irish Land Purchase Act, or similar laws;
• a Purchase and Sale Agreement, as a contract between a buyer and seller of land (real estate).

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.