Dear Cecil: What do the letters K, R, and U mean on various food and other packages? For example, Chun King Rice has a small letter K, Clorox Scrub Cleaner a U, Dow's Ziploc storage bags a U, and so on. Frank N., Baltimore

Cecil replies:

The circled R, as I think most people know, stands for registered trademark. The K, circled K, and the circled U are all meant to indicate the product is kosher. Therefore, Frank, what you have in your closet there is a box of kosher storage bags. This may strike you as taking this kosher business a bit far, but allow me to explain.

A product is “kosher” if a rabbi determines and certifies that it meets the requirements of Jewish dietary law, which is no mean feat in these days of additive-laden prepackaged foods. In addition to the familiar prohibitions against pork and mixing meat and dairy substances, the law contains strict provisions for the slaughter and preparation of virtually all animal products. The most innocent-looking ingredient–an emulsifier, an oil, a dab of gelatin–can mean the difference between kosher and nonkosher, even if it merely comes in contact with something that will eventually be eaten (which is where things like oven cleaners and plastic bags come into play).

Because some rabbis are more finicky (or more thorough, depending on how you look at it) about enforcing these strictures than others, the matter of who is doing the certifying is a matter of some moment. Thus we have a plethora of codes signifying kosherness.

The unadorned K, being a simple letter of the alphabet, can be used by anyone who wants to claim his product is kosher. The circled K, on the other hand, is a registered mark and can only be used with the permission of its owner, the Organized Kashruth Laboratories of New York, a private certifying concern. The circled U is similarly controlled by the Union of Orthodox Jewish Congregations of America, the undisputed heavyweight of kosher-certifying organizations.

Some smaller organizations have marks that you may find on locally-distributed products. It’s not a matter of one product being more or less kosher than another, but who says so and whom you want to believe.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.