Hi Barbara,

According to Kikkoman their Teriyaki Sauce is:
A blend of our naturally brewed soy sauce, wine, corn syrup and select spices, it has a depth of flavor that makes it an ideal marinade or brush-on sauce, right from the bottle. It adds a delicate sweetness to grilled, broiled, roasted or braised foods, either before, during or after cooking.

If your recipe only calls for a teaspoon or two of Teriyaki Sauce you probably won't notice a difference using the soy sauce instead. If it's a major ingredient in the recipe then you may want to add a small amount of rice wine (if you have it) and sweetener or just sweetener (sugar, light corn syrup, or honey).

Happy Cooking!

Betsy