The term fish refers to any aquatic animal with gills, fins and a streamlined body. It is used as a common name for various species of marine or freshwater animals belonging to the class Actinopterygii, which includes many types of bony fish such as salmon, trout, bass, cod, etc., as well as cartilaginous fish like sharks and rays. However, in some contexts, it may also refer to other marine or freshwater animals that do not have gills, but instead breathe through specialized respiratory organs such as lungs (e.g., mudskippers) or skin (e.g., lungfish).