The word "teriyaki" originally described a style of cooking; it refers to meat or fish basted with a sweet and salty sauce and roasted on a grill or over an open fire. The sauce is traditionally made with soy sauce and two types of rice wine, mirin and sake. Today the word is just as readily used to describe the sauce as the cooking style.
"Teriyaki" contains the nut of both ideas. "Teri" comes from "tare", a word meaning luster or glaze, and it describes the glossy sheen the sauce provides. What we call teriyaki sauce is one of a number of sauces collectively referred to as "tare" in Japan. "Yaki" refers to cooking over direct heat—a fundamental concept that also shows up in the words yakisoba, yakitori, okonomoyaki, teppanyaki, sukiyaki, and many more.
The sauce and the way it's used are essentially inseparable concepts in Japanese cooking. One can't cook something "teriyaki style" without the sauce, and one wouldn't use teriyaki sauce in any other way. According to the oldest surviving writing on the subject, teriyaki dates back at least as far as the early 19th century—the late Edo period in Japan. William Shurtleff and Akiko Aoyagi, authors of A History of Soy Sauce, note that a glaze of soy sauce, mirin, and sake was used in recipes for charcoal-baked eel before the term "teriyaki" was coined.
In a seminal book on Japanese cuisine, the aptly named Japanese Cooking, celebrated chef Shizuo Tsuji offered a simple recipe for the sauce: seven tablespoons of dark soy sauce, seven tablespoons of mirin, seven tablespoons of sake, and one tablespoon of sugar, boiled in a saucepan until the sugar dissolves. We have our own tried-and-tested teriyaki recipe that's lighter on the sake and heavier on the sugar. The "gloss" of teriyaki comes primarily from the mirin, a syrupy rice wine.
In Japan, teriyaki is traditionally used to flavor grilled seafood. The Japanese favor fatty seafood like tuna, yellowtail, or the aforementioned eel, because the crisp fat of grilled seafood tastes fantastic with the salty-sweet flavor of teriyaki. Seafood teriyaki might once have been roasted on skewers over a fire, but a charcoal grill now serves the same purpose. Tsuji suggested adding the sauce to a frying pan in the late stages of cooking. This provides a beautiful, shiny glaze that coats the ingredients with color and flavor, and helps the sugar in the sauce avoid burning.
In the West, teriyaki is popularly used to prepare salmon, beef, or chicken, and the ingredients in the sauce are a little different. It's also often used as a dip for potstickers. Teriyaki is meant to be a cooking sauce, not a table sauce, but it's perfectly safe to use as a dip or a condiment. Western teriyaki often doesn't contain sake, and sometimes doesn't even contain mirin, but it may include additional flavorings like minced garlic, minced ginger, or toasted sesame oil, and more sugar or other sweeteners like honey.
The Westernized version of teriyaki probably came to us via Japanese immigrants to Hawaii, where brown sugar is much more commonly available than rice. Hawaiian teriyaki also sometimes contains pineapple juice or green onions. (The enzyme bromelain in pineapple juice is a useful addition to a marinade, as it tenderizes red meat.) This version of teriyaki is now a popular part of Hawaiian cuisine; the sauce served at a luau is more likely to be teriyaki than American-style barbecue sauce.
Kikkoman, the world-famous Japanese soy sauce company, cites Hawaiian teriyaki as the inspiration for the bottled teriyaki sauce that it introduced to the American market in 1961. Years later the company introduced a second version of teriyaki that used corn starch (now "modified food starch") to create a much thicker basting sauce. Other manufacturers followed suit, and thicker teriyaki is now a common sight in supermarkets. Its viscosity made teriyaki more popular as a dipping sauce, and even as a table sauce like ketchup.
Home cooks should be aware of the two versions of teriyaki sauce when they go shopping. The thinner teriyaki sauce makes for a better a marinade, though in our teriyaki taste test, we determined you're better off making your own teriyaki marinade at home than buying a bottle of the thin stuff. The thicker American-style teriyaki sauce is a wiser purchase. It's more of an instant flavor enhancer, and better for basting as you cook. The high sugar content means it can create a lovely thick caramelized coating.
In addition to using teriyaki sauce as a baste, a marinade, and, yes, a dipping sauce for your potstickers, it's also great in a stir fry or mixed into ground meat for burgers, and it's a great base for a chicken wing recipe. If you want a basting teriyaki and accidentally bought one that's too thin, you can mix it with a little butter.
The names on the labels are often interchangeable, so how do you tell the difference between thin and thick teriyaki sauces? The thinner sauce may be labelled as a marinade and the thicker sauce may be labelled as a grilling sauce, but some brands claim to be both. Your safest bet may be to tip the bottle and see how the sauce moves. The recommended uses on the label may also give some tips, and of course you can look for starch in the ingredients list. If there's no starch, it's a marinade.
Whichever version you buy, it will last a good long while. In theory, authentic teriyaki sauce never goes bad. Some eel houses in Japan have kept tubs of teriyaki sauce going for centuries by topping them up rather than replacing them. But in practice, the label probably gives you about six weeks if you keep the bottle in the refrigerator.