If milk comes from a plant, can you still call it milk?

Not according to the dairy industry. Facing growing competition from dairy alternatives like almond, soy and coconut milk, the nation’s dairy farmers are fighting back, with an assist from Congress. Their goal: to stop companies from calling their plant-based products yogurt, milk or cheese. Dairy farmers say the practice misleads consumers into thinking that nondairy milk is nutritionally similar to cow’s milk.

A bipartisan group of 32 members of Congress is asking the Food and Drug Administration to crack down on companies that call plant-based beverages “milk.” They say F.D.A. regulations define milk as a “lacteal secretion” obtained by milking “one or more healthy cows.” Proposed legislation from Representative Peter Welch, Democrat of Vermont, and Senator Tammy Baldwin, Democrat of Wisconsin, a state known for its cheese, suggests a slightly broader definition. Their bill would require the F.D.A. to target milk, yogurt and cheese products that do not contain milk from “hooved mammals.”

“The bottom line for us is that milk is defined by the F.D.A., and we’re saying to the F.D.A.: Enforce your definition,” Mr. Welch said.

But critics say consumers know exactly what they are buying when they choose almond or soy milk instead of dairy milk. “There’s no cow on any of these containers of almond milk or soy milk,” said Michele Simon, executive director of the Plant Based Foods Association, a trade group representing 70 companies. “No one is trying to fool consumers. All they’re trying to do is create a better alternative for people who are looking for that option.”