A majority of Americans are in the minority, legally speaking.

It's the kind of paradox that only a lawyer could love, but it's right there in the regulations that define the concept of "minority" for the purposes of federal anti-discrimination laws. The number of people included in "minority" or "protected" classes under the federal rules is clearly a majority of the population.

Among those covered by one or more provisions of the regulations:

All females.

All blacks.

All those of Spanish, Asian, Pacific island, American Indian or Eskimo ancestry.

All Vietnam-era veterans.

All presently or formerly handicapped.

All workers between the ages of 40 and 64 (and most of those between 65 and 70).

"Members of various religious and ethnic groups... such as Jews, Catholics, Italians, Greeks, and Slavic groups."

No one, in or out of government, seems to know for sure how many Americans are protected as "minority group members," because the categor ies overlap and because there is no definite measure for some classes.

The Labor Department says that estimates of the number of handicapped Americans, for example, range from 35 million to more than 60 million.

It is obvious, though, that a majority of the population is in the protected categories, because females constitute more than half of the population.

More important, since most antidiscrimination laws deal with employment, is that a majority of the work force falls into one or more minority categories. The civilian work force, numbering 102.5 million people, is about 60 percent male.

"When you consider all the (minority) headings, though," says Anne Marshall, a public information specialist at the Equal Employment Opportunity Commission, "It's obvious that a majority of the work force is covered by the regulations."

Not all minorities are equal, at least in terms of the protection they are entitled to under federal rules. The first five categories set forth above are entitled to "affirmative action" in employment -- that is, employers must establish goals and timetables for hiring and promoting members of those classes, and must give them prefer ence over "nonminority" applicants who are equally qualified.

Workers over 40, however, and "members of various religious and ethnic groups" are entitled to "special consideration" and "outreach," both of which fall short of the rules governing "affirmative action."

The policy of specifying a minority group that needs particular protection goes back at least to the Reconstruction era, when laws and constitutional amendments were adopted to protect blacks from discrimination.

The range of protected minorities began to grow noticeably in the 1960s as federal agencies developed regulations to implement the various civil rights laws passed then.

Since 1967, Congress has passed a series of statutes setting up specific safeguards for specific minorities.

The Age Discrimination in Employment Act of 1967 made it illegal to pass over an applicant aged 40-64 for employment or promotion because of his age, and outlawed mandatory retirement for workers under 65. The law was extended last year to include most workers up to age 70.

In a series of veterans' bills, most recently the Vietnam Era Veterans Readjustment Assistance Act of 1974, Congress required many employers to give Vietnam era veterans, and disabled veterans of any era, affirmative action rights in hiring and promotion.

In the Rehabilitation Act of 1973, Congress established a similar affirmative action requirement for the handicapped. This statute caused particular problems for the regulation-writers, because Congress had been vague about what constitutes a handicap. The Department of Health, Education, and Welfare eventually came up with an expansive definition that includes, among other conditions, drug addiction and alcoholism.

Shen employers squawked at the notion of setting goals and timetables for the hiring of drug addicts, the department issued a clarifying regulation noting that "while an alcoholic or drug adict may not be... disqualified for employment solely because of his or her condition, the behavorial manifestations of the condition may be taken into account in determing whether he or she is qualified."

Some lawyers say the expansion of the minority class has spawned confusion and some tension as members of the traditional minority groups discover that a mojority of their competi tors for jobs and services have acquired the same legal protection. The Equal Employment Opportunity Commission, these lawyers note, has begun receiving complaints in which an employer, school or provider of services is accused of favoring one protected minority at the expense of others.

Some civil rights lawyers are concerned, too, that the growth of the legal "minority" has undermined the statutory goal of protecting certain elements of society against majority prejudice.

Supreme Court Justice Lewis Powell expressed both of these fears in his opinion upholding the concept of affirmative action in last year's Bakke decision.

"Disparate constitutional tolerance of such classifications well may serve to exacerbate racial and ethnic antag onisms rather than alleviate them," Powell wrote.

"Not all of these [minority] groups can reveive preferential treatment... for then the only 'majority' left would be a new minority of white Anglo-Saxon Protestants."

At the Labor Department, which issues and enforces many of the government's minority protection regulations, there seems to be no serious fear of such consequences.

Explaining the department's various affirmative action rules recently, Laura Fox, of Labor's Employment Standards Office, said that, "The first rule is that an employer only has to hire the most qualified applicant.

"If it gets down to five people and they're all equally qualified," Fox said, "and they're all from protected classes, then the employer sees which classes are already represented in his work force, and he would not hire an applicant from those classes. He'd hire from an under-represented class.

"That's not discrimination," Fox said. "That's just giving one person a job and turning down another one."