A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land apart from a river, stream, or other form of moving water that serves to feed or drain the lake. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams, which are usually flowing. However most lakes are fed and drained by rivers and streams.

Natural lakes are generally found in mountainous areas, rift zones, and areas with ongoing glaciation. Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world there are many lakes because of chaotic drainage patterns left over from the last Ice Age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.

Many lakes are artificial and are constructed for industrial or agricultural use, for hydro-electric power generation or domestic water supply, or for aesthetic or recreational purposes.

Athanasius Kircher (1601 or 1602–1680) (sometimes erroneously spelled Kirchner) was a 17th century German Jesuit scholar who published around 40 works, most notably in the fields of oriental studies, geology, and medicine. Kircher has been compared to fellow Jesuit Roger Boscovich and to Leonardo da Vinci for his enormous range of interests, and has been honoured with the title "master of a hundred arts".

Kircher was the most famous "decipherer" of hieroglyphs of his day, although most of his assumptions and "translations" in this field have since been disproved as nonsensical. However, he did make an early study of Egyptian hieroglyphs, correctly establishing the link between the ancient Egyptian language and the Coptic language, for which he has been considered the founder of Egyptology. He was also fascinated with Sinology, and wrote an encyclopedia of China, in which he noted the early presence of Nestorian Christians but also attempted to establish more tenuous links with Egypt and Christianity.