It is intended that this research will set up operational definitions of style and will study the fundamental phenomenon of style. Four experiments were conducted. In Experiment 1, college students were asked to sort out pictures of buildings having the same style to test operational definition. The results showed that style is recognized by the common features present in pictures. The term "common features" refers to the same physical forms appearing in many design products created by a designer. In Experiment 2, students were asked to sort out pictures into four resemblance scales to test the degree of style. The results showed that the degree of style is in proportion to the number of common features present. In Experiment 3, an architectural historian identified a style in pictures that had various feature combinations in order to observe the measurement of style, which refers to the threshold for recognizing a style. Data showed that three features are the lower bound for style recognition. Experiment 4 tested the degree of distortion in order to measure the recognizability of a stylistic feature. An expert was asked to recognize distorted pictures, and results showed that beyond 40% geometric distortion a feature is no longer the label of the style. Observations made in this study suggest that if an artifact has at least three features attributing to a designer, an individual style exists. If four features repeat in a minimum of three different artifacts, an individual style is visible.