The word tuna dates back only to 1880 in print and is attributed as a Spanish American derivation of the English counterpart, tunny. It is derived from the Latin Thunnus, the name of its scientific genus. Tuna has been fished from the warm, temperate parts of the Mediterranean Sea and the Pacific, Atlantic, and Indian Oceans since ancient times. As a member of the mackeral family, tuna naturally has a stronger, more robust flavor than whitefish.

Tuna has oil in the flesh, which is darker than in white fish. It is rich in polyunsaturated fatty acids and has more B vitamins than white fish. It is also a good source of vitamins A and D and a good source of protein and iodine. The flesh of the tuna can range from very light pink (nearly white) to deep reddish brown, depending on the variety. Prime raw tuna steaks look very much like raw beef, right down to the deep red color of the flesh. The tuna steak may have a darker brown area, which is edible but has a much stronger flavor. Sometimes this is already trimmed away by the fishmonger. Fresh tuna is usually sold already skinned since the skin is extremely tough.

When selecting fresh tuna, avoid any with dry or brown spots (other than the natural darker brown area). There should be no rainbow sheen on the fish and should smell ocean-fresh. The fishmonger generally keeps the tuna in a large filet which looks very much like a beef loin and will slice off what you need. Fresh tuna season runs from late spring to early fall, but frozen steaks are available year-round.