(Bloomberg) — How much investing jargon do youneed to master while saving for retirement?

The word “fiduciary” is a good example. AFinancial Engines survey releasedThursday finds that only 18 percent of Americans are sure whatthe word means.

That kind of ignorance can be expensive: U.S. financialadvisers are divided between “fiduciaries” required to putyour interests first (like a doctor or lawyer), and otherslike brokers, more akin to salespeople, required only to push“suitable” products that may profit them more than you.

Judy McChester-Nedd, a 59-year-old retired executive in Helena,Ala., didn't know the difference when she hired an adviserunconstrained by fiduciary duty. She says she asked for aconservative strategy and ended up losing 14 percent last yearin actively managed mutual funds.

Read: Our coverage of the proposed DOL fiduciaryrule

Ian MacGregor, 38, is a consultant in Dublin, Ohio, whoalso didn't know the difference. His adviser kept steering him intomutual funds with upfront load fees of asmuch as 5 percent. (There's another nugget of jargon youshould know: A load is a one-time charge to invest ina fund. In other words, front-end load funds areinvestments where you lose money the moment you buythem.)

Nonfiduciary advisers are free to recommend only the productsthat earn them the highest commissions, which can come from bothload fees and annual fees.

Because they get paid in so many complicated ways, it can behard to tell how much they're making off you and what theirincentives are. Fiduciary advisers tend to get paid in moretransparent ways, often by charging an annual fee based on theassets they manage.

Of course, not all nonfiduciary advisers charge high fees orpush lousy bets, and fiduciary advisers aren't all perfect.But it's hard to invest when you're not sure whomto trust.

“I've lost confidence,” McChester-Nedd says. “The governmentneeds greater oversight over this because regular people aregetting hurt.”

MacGregor agrees: “There's got to be some way to protect theless-savvy investor from being taken for a ride.”

Well, they may get their wish. Despite years ofresistance from Wall Street, the U.S. Department of Labor isexpected to announce soon the final version of a rulethat may force financial advisers to abandon the way they'vedone business for decades. For the first time, all advisersmay need to act as fiduciaries, putting their clients'interests first when handling retirement accounts.

The rule could clear up some confusion. According to the surveyof more than 1,000 people paid for by Financial Engines (afiduciary advisory firm), 46 percent of Americans incorrectlybelieve that advisers already “are legally required to put the bestinterests of their clients first” when dealing with retirementassets.

The majority of respondents, 54 percent, knew advisersweren't under that requirement, but they sure weren't happy aboutit. Overall, 93 percent said it's important that all advisers putclients' interests first when providing retirement advice.

Wall Street counters that a strong fiduciary rule willmake it less profitable to offer advice to lower- and middle-incomeAmericans. “This proposal, if enacted, would limit the abilityof Americans to continue to receive personalized investmentguidance for retirement plan accounts, which would result in a lesssecure retirement for many,” Kenneth Bentsen Jr., chief executiveof the Securities Industry & Financial MarketsAssociation, an industry group, wrote in one of more than 3,000comments on the proposed “conflict of interest” rule last year.

Advocates of the rule say it may generate new insurance andinvestment business models that cost less and aren't as likely toexploit the unsophisticated.

“The marketplace was changing anyway,” says Mitchell Caplan, CEOof Jefferson National, an insurance company which sellsproducts to fiduciary advisers. He predicts that, in thefuture, technology will help fiduciary advisers servemore clients more efficiently. “There will be lots ofcompanies and business models that continue to evolve,” hesays.

Much depends on how the final rule is implemented. In theinitial proposal, firms handling retirement accounts needed to signa contract with clients making clear they'd put their interestsfirst. Figuring out what this means exactly may take a while, ascourts could end up being the final arbiter of the rule'slanguage. It's also not clear how the final rule would be enforced,though it might leave noncomplying firms open to penalties orlawsuits.

Whatever regulators and judges decide, many investors havealready made a clear choice, as the number of investorswilling to pay load fees has plunged:

MacGregor is among them, having switched his account to afiduciary adviser charging him 0.5 percent peryear. McChester-Nedd moved her money into cash and is stillfiguring out what to do with it. “This stuff is very complicated,”she says, adding she's “bewildered” by “inconsistent andinaccurate” information.

McChester-Nedd is confident, though, that she'll figure it outeventually. Still, she worries about friends and familywithout her business background: “They're totally at the mercy ofthe system.”

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