Component dependency is an important software measure. It is directly related to software understandability,maintainability, and reusability. Two important parameters in describing component dependency are the type of couplingbetween two components and the type of the dependent component. Depending upon the different types of coupling and thetype of the dependent components, there can be different effects on component maintenance and component reuse. In thispaper, we divide dependent components into three types. We then classify various component dependencies and analyzetheir effects on maintenance and reuse. Based on the classification, we present a dependency metric and validate it on 11open-source Java components. Our study shows that a strong correlation exists between the measurement of the dependencyof the component and the effort to reuse the component. This indicates that the classification of component dependencyand the suggested metric could be further used to represent other external software quality factors.