T1he term volunteer is used too broadly in denoting nonsalaried service. In this article, the authors attempt to delineate the boundaries of the term volunteer. They first reviewed 11 widely used definitions of volunteer. Using a content analysis, they identified four key dimensions commonly found in most definitions of volunteer. They then proposed an internal continuum (Guttman scale) for each dimension that distinguished between "pure" and "broadly defined" volunteers. They analyzed the importance of these dimensions in determining how people perceive what makes a volunteer. They expanded this analysis by introducing and exemplifying the concept of the net cost of volunteering. They developed a 21-item instrument and asked 514 respondents to assess the extent to which each item represented their perceptions of a volunteer. Their findings support the dimensions and their continuum as well as the importance of net cost as a basis for public perceptions of what makes a volunteer.