Science, any system of knowledge that is concerned with the physical world and its phenomena and that entails unbiased observations and systematic experimentation. In general, a science involves a pursuit of knowledge covering general truths or the operations of fundamental laws.
When did science begin?
Observing the natural world and paying attention to its patterns has been part of human history from the very beginning. However, studying nature to understand it purely for its own sake seems to have had its start among the pre-Socratic philosophers of the 6th century BCE, such as Thales and Anaximander.