The Scientific Revolution along with the ideas coming from the intellectual movement of Enlightenment gradually led to a different conception of the world and to a redefinition of the scientific methodology. The world at this period was perceived as a machine regulated by natural laws. Methodology and discoveries of Copernicus and Galileo were the forerunner of the significant changes that were going to appear in methodology of natural sciences. Scientists of 17th and 18th century started investigating the world systematically through experimentation, logic and mathematics, which contributed to the formulation of laws. These conditions favored the utilization of scientific techniques, mechanisms and models that contributed to understanding, explaining and describing the natural world and also to drawing of scientific inferences. An interesting example is the mechanism of similarity, which seems to be recognized after the Scientific Revolution, and its systematic exploitation extended significantly after the 19th century through the technique of scientific models, mainly in the fields of Engineering and Physics. Notions of similarity and similar systems were rapidly evolved after the 17th century. This fact leads to the following important question: How did the Scientific Revolution and the Enlightenment influence the evolution of these concepts? The concept of similar systems has been identified in Galileo's theories, but it was introduced by Newton, who defined the similar systems mainly based on geometrically 2 similar configurations, similar movements between particles and similar paths in proportional times. In 1914, the American physicist Edgar Buckingham proposed the term ‘‘physically similar systems’’ in order to replace Newton's previously widely accepted term, ‘‘similar systems’’. Buckingham focused on physical similarity. He argued that two physical systems are similar if there is a proportional relation between two corresponding quantities, which can be described by the same equation. At the beginning of the 21st century, the American philosopher Susan G. Sterrett highlights the significance of similarity, of similar systems and scientific models in the field of Philosophy of Science. Sterrett accepts that the concept of similarity is related to the concept of ratio and she understands the concept of physical similarity as a generalization of the concept of geometrical similarity. Her contribution to the evolution of the concept of similarity is detected in her argument that similarity is always defined in the light of a scientific hypothesis. Therefore, the similarity between a model and an object of interest is usually not absolute, as it is always defined with respect to particular characteristics. In addition, Sterrett argues that similarity is a function mechanism of analogue models, which are used to draw inferences, observations or predictions about similar set-ups that scientists cannot observe.