The C.D.C. is sending a tobacco-use survey to 20,000 students nationwide that asks about e-cigarette experimentation but does not identify the devices by other names. The state of California, through a nonprofit partner called WestEd, is asking virtually the same question of 400,000 students.

Brian King, senior adviser to the Office on Smoking and Health at the C.D.C., said the agency was aware of the language problem. “The use of hookah pens could lead us to underestimate overall use of nicotine-delivery devices,” he said. A similar problem occurred when certain smokeless tobacco products were marketed as snus.

Other health officials are more blunt.

“Asking about e-cigarettes is a waste of time. Twelve months ago, that was the question to be asking,” said Janine Saunders, head of tobacco use prevention education in Alameda County in Northern California.

In October, Ms. Saunders convened a student advisory board to discuss how to approach “e-cigs.” “They said: ‘What’s an e-cig?’ “ Ms. Saunders recalled, and she showed what she meant. “They said: ‘That’s a vape pen.’ “

Health officials worry that such views will lead to increased nicotine use and, possibly, prompt some people to graduate to cigarettes. The Food and Drug Administration is preparing to issue regulations that would give the agency control over e-cigarettes, which have grown explosively virtually free of any federal oversight. Sales of e-cigarettes more than doubled last year from 2012, to $1.7 billion, according to Wells Fargo Securities, and in the next decade, consumption of e-cigarettes could outstrip that of conventional cigarettes. The number of stores that sell them has quadrupled in just the last year, according to the Smoke Free Alternatives Trade Association, an e-cigarette industry trade group.

The emergence of hookah pens and other products and nicknames seems to suggest the market is growing well beyond smokers. Ms. Zacks was among more than 300 Bay Area high school students who attended a conference focused on health issues last month on the campus of the University of California, Berkeley. Many students talked about wide use of e-hookahs or vaping pens — saying as many as half of their classmates had tried one — but said that there was little use of e-cigarettes.