Scientists are people who engage in systematic activities to acquire knowledge describing and predicting the natural world. In a more strict sense, scientists can refer to individuals who use scientific methods. The person may be an expert in one or more fields of science. The term scientist was coined by theologian, philosopher and historian of science William Whewell. This paper focuses on the more strict use of the word. Scientists conduct research to gain a more comprehensive understanding of nature, including physical, mathematical and social fields.

Today, philosophy is generally regarded as a distinct activity from science, although these activities are not always distinguished in this way. Before modern times, science was regarded as a "branch" of philosophy rather than the opposite. The aim of philosophers is to provide a comprehensive understanding of the basic aspects of reality and experience, usually through conceptual rather than empirical methods. Natural science research is usually different from inquiry in humanities, and it is also different from inquiry in social science and Mathematics for various reasons, although these differences may cause controversy.

Scientists are also different from engineers, who design, manufacture and maintain equipment for specific situations. However, without a lot of research on science and scientific methods, no engineer can get the title. When science aims at practicality, it is called applied science. Applied scientists may not be designing something specifically, but conducting research aimed at developing new technologies and practical methods. When science tries to answer questions about the fundamentals of reality, it is sometimes called natural philosophy, which was well known before the 19th century.