Memos and circulars are both fixtures of the business world. A memo displays somewhat limited content. Often, they are used as sort of a concise to-do list. In other words, they inspire action to do something. Someone can also pass a proposal or idea by issuing a memo. In a corporate environment, a memo can serve as a form or message from the top of the ladder. A circular, on the other hand, usually addresses several topics.
Circulars also cover general subject affairs. A circular possesses a broader distribution to a larger reader contingent because it serves more like a general announcement. Circulars are typically used for advertising purposes so that an agency, company, or firm can issue a formal public statement. Today, most messages are conveyed electronically through email and the use of computers.