Yours is a wonderful question with no real answer. Why is there no answer? Because no one can agree on what a relish - cranberry or otherwise - is.... (There's not a whole lot of agreement on chutney either, by the way.)

Our generally useful dictionary says a relish is, "any of a variety of foods, as pickles, olives, piccalilli, or raw vegetables, served with a meal to add flavor or as an appetizer; or a pickled condiment, usually with ... spices, sugar, vinegar, etc."

A chutney is, "a relish made of fruits ... spices, herbs, and sugar, with vinegar or lemon juice." This definition entirely misses the Indian origin of chutney, and also the fact that a traditional chutney is generally sour. As they moved into other cultures (notably British), chutneys became a good deal sweeter.

The fact is, there are zillions of relishes and chutneys (and by this point you've noticed that, by definition, a chutney is a relish). After scouring dozens of cookbooks, we feel safe making this generalization - a chutney featuring a particular ingredient is going to be more savory, tart, and/or sour than a relish featuring the same ingredient.

So you can certainly use the cranberry chutney you've found, but it is likely to be more assertive than what your sweet-potato-recipe-writer had in mind. If you can't find a store-bought cranberry relish, you can easily make your own.

A lot of cookbooks have recipes for uncooked cranberry relish, generally including oranges, spices, and nuts. But Christopher Kimball, author of The Yellow Farmhouse Cookbook and publisher of Cook's Illustrated, says, "I am not a big fan of uncooked relishes or chutneys for the holidays. Some recipes call for throwing everything into a food processor, including whole oranges, pulsing, and that's it. Cooking blends the flavors and also dissolves the sugar."

Here is a recipe for a cooked cranberry relish, and, for contrast, the one for Kimball's Cranberry Chutney.