In some cases, Avicenna used the semantical premises in order to deduce some conclusions in his Physics. For instance, he analyzes five derivatives of the word “tabiat” and then in the light of these analyses, he concludes that the natural properties of an object are caused by its essence and are based on it. Here, the major problem is how to justify Avicenna's passage from semantical premises to physical consequents. This paper shows that through analyzing the relation between nature and (...) its derivatives, on one hand, and explicating Avicenna’s definition of the “nature” on the other hand, we can defend the rationality of such a passage. (shrink)