Any fuel derived from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are non-renewable, and their burning generates the greenhouse gas carbon dioxide.

plural of trace fossil

Any ancient remains of a plant or animal that lived during a specific geological period and that can be used to date the containing rocks.

(evolutionary theory) Any species discovered first as a fossil and believed extinct, but which is later found living; an organism that has remained unchanged over geological periods.

(paleontology) A type of fossil reflecting the reworking of sediments and hard substrates by organisms, rather than the physical remains of the organism itself. This includes structures such as burrows, trails, impressions, coprolites and borings.

(mineralogy) copaline

(linguistics) A word that is broadly obsolete but remains in current use because it is contained within an idiom that is still in use.

plural of fossil word

A fossil containing part of an organism's body, as opposed to a trace fossil.

plural of fossil fuel