Adaptation is the process that makes organisms better suited to their habitat.[158][159] Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term adaptation for the evolutionary process and adaptive trait for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection.[160] The following definitions are due to Theodosius Dobzhansky.