common names used to refer to various small, oily forage fish within the herring family of Clupeidae
A school of sardines in the ocean

Sardine is a name of several kinds of fish, especially oily fish. Another name for these fish is Pilchard. All of those fish are quite small and are related to the herring. The Latin name of the family of these fish is Clupeidae. However, the naming is not precise. Fishbase, a database about all kinds of fish, has six species just named pilchard. There are over a dozen with the name of sardine. Many more exist, with the basic names qualified by adjectives.

The fish are named after the Island of Sardinia. In the past, they could easily be fished there.

Many shops and supermarkets sell canned (or tinned) sardines. Very often, those fish are not sardines, but rather sprats or round herrings.