This chapter considers an oversimplified model of an antenna with a wire having a specific length and negligible cross section and carrying a current density flowing in a specific direction. Even though this model is oversimplified, it possesses many of the significant characteristics of a real antenna. The chapter discusses geometry of linear antenna and radiation pattern produced by a short antenna and intermediate length antenna. The model of the antenna is greatly oversimplified and the results greatly de-emphasize the importance of radiation into the side lobes. The chapter considers a more realistic model called a center fed, linear antenna. Therefore, such an antenna is most useful in the half- or full-wave regime.