A fossil is the preserved remains or traces of a living thing from the distant past. Scientists usually keep the word for things older than about 10,000 years, roughly the end of the last ice age. That is a convention, not a hard rule.

There are two big kinds:

• Body fossils are parts of the living thing itself: bones, teeth, shells, wood, leaves.
• Trace fossils (also called ichnofossils) are evidence of what a living thing did: footprints and trackways, burrows, bite marks, eggs, nests, and coprolites, which are fossilised droppings.