What qualifies as a small business?

A small business may be defined as a business with a small number of employees. The legal definition of “small” may vary by state or industry but is generally under 100 employees. These businesses are normally privately owned corporations, partnerships, or sole proprietorships. The smallest businesses, often located in private homes, are called home-based businesses or microenterprises, or SoHos (Small Office/Home Office). The term “mom and pop business” is a common expression for a single-family operated business without any hired labor, e.g., “mom and pop store.” Source: http://wikipedia.org.
The Small Business Administration defines a small business concern as “one that is independently owned and operated and which is not dominant in its field of operation.” It is important to note that the definition will vary from industry to industry and from state to state. This numerical definition is the “size standard” and is almost always stated in terms of either number of employees or average annual receipts.
Source: Small Business Administration