Ten years ago, in the spring of 1970, Georgetown University launched a modest program in adult education -- 79 students enrolled in five courses.

As the decade draws to a close that program has grown into the largest single division of the university, and therein lies a tale of the 1970s.

The estimated 7,000 adults now enrolled in 600 courses offered annually in Georgetown's school of continuing education already outnumber the university's 5,864 undergraduates, and there are no indications the program has stopped growing.

Its curriculum ranges from classical music appreciation to foreign languages, and the 14 foreign languages offered this year -- including Gaelic and Lithuanian -- outnumber what's available in the regular undergraduate curriculum.

The program grosses about $1 million a year, and it clears approximately $120,000 after expenses.

The Georgetown experience illustrates what many educators feel may be the single most significant development in higher education occurring during the 1970s and 1980s: that adult, part-time college students are fast becoming a new majority.

More than three-fourths of the nation's 2,900 colleges and universities offered adult education programs in 1978, more than twice the number offering them a decade before in what the national Center for Educational Statistics calls a continuing upward trend.

More than 18 million adults were enrolled in adult education programs in 1978, the latest year statistics are available. In 1975 the total was 16 million.

On campuses in the Washington area and across the nation, the adult presence is forcing a redefinition of the mission of higher education.

No longer, notes George Johnson president of Fairfax County's George Mason University is college mainly a mechanism for assimilating 18-year-olds into the mainstream of America culture.

What it is becoming instead, he says, is a shared experience in which 18-year-olds, senior citizens, people changining careers, middle-aged women with grown children, people seeking new skills or self-enrichment and people with spare time on their hands are coming together in the college class room for a variety of diverse purposes.

"It's the future of higher education," says Robert Hawkes, dean of the division of continuing education at George Mason, where more than 60 percent of the 13.500 enrollees are adult part-time students.

"In the decade of the 1980s, the typical American will come to accept formal learning as something you do as long as you live."

Virtually every college in the Washington area has topped the adult market to one degree or another. At American University, for example, adult education is being promoted with a catchy "Jog Your Mind" advertising campaign in newspapers and on radio. AU has opened satellite centers in Montgomery and Fairfax counties and pushes its courses with the direct mailings. Director Thomas Coffey sees a steady 10 to 20 percent annual growth in the adult program. Within a few years, he predicts, adult part-timers enrolled at AU will outnumber the 4,500 traditional undergraduates.

George Washington University's college of general studies, the adult education arm, takes in about $6 million a year from 7,000 students -- about 13 percent of the total $47.5 million the university collects in student fees. It clears $1 million after expenses.

"Continuing education today," said the National Advisory Council on Extension and Continuing Education in a report this fall, "is very much a product of a more affluent society and is conducted almost university by academic institutions as a propietary exercise.

"The average participant in postsecondary continuing education is also white, relatively affluent, educated and employed."

For the colleges as institutions, pursuit of the adult market is not only a question of making money; it is a matter of survival.

The baby boom that followed World War II peaked in 1961, and those babies, 4.3 million of them, turned 18 in 1979. During the coming decade, the number of 18-year-olds will plummet 21 percent to 3.4 million in 1990, and most projections call for this decline to continue through the end of the century.

Acutely aware that the enrollment declines already have forced closings of elementary and junior high schools, colleges know they face the same fate during the 1980s unless they can find some way to fill the gap. They have turned to the adult student as the logical solution.

To tap that market they have launched advertising and promotional campaigns, redesigned curricula and degree requirements, scheduled clases at a variety of off-campus locations for their students' convenience and arranged for courses to meet early in the morning, late at night and on weekends.

At American University adults can earn up to 30 credits for such nonacademic learning experiences as on-the-job training programs and employment assignments providing they can measure up to certain standards.

"It's a good program. It gets you out of repeating the things you're already proficient in," said Victor Taylor, 37, a computer programmer who received 30 credits from AU for engineering and geological surveying experience in the Mideast and on the Alaska oil pipline.

Working full time and studying part time, Taylor is aiming towards a degree in physics and statistics "without having to do six hours a semester for eight years."

"The difference between not having a degree and having a degree," says Taylor, is the difference between being a technician and being an engineer. "You get more money with the degree."

But it is more than the need for credentials that is drawing adults back to college.

Consider for example, Dr. Daniel Cowell, 45, a psychiatrist with the U.S. Public Health Service. For the last two years, Cowell has been spending one night a week at Georgetown pursuing a variety of courses that have ranged form international politics to comparative religion.

"It seemed an excellent way for me to meet some of my nonvocational needs," said Cowell. "I've never really lost an interest in the classics, history, political science, sociology and the arts. This won't add one whit to my vocational value, although I do believe a broad understanding of societal movements in today's world is important to any thinking adult."

Or take the large and growing corps of middle-aged women returning to college after having raised families.

At 46, Charlotte Stannard, 22 years after graduating from San Jose State, is studying for a degree in guidance and counseling at Georgetown Mason University.

"My oldest daughter decided to get married and my second daughter is in California," said Stannard. "All of a sudden I was faced with one child at home. I thought, 'Hey what about me?' Everyone else was going and growing and I was just staying right here.

"I had been a Girl Scout leader and a Cub Scout leader. My family was my whole identity and now I was faced with this thing where everybody was leaving. It felt like being out of a job. It's going back to school, but you learn a lot about youself and you find that you do have marketable skills."

But of all the postsecondary educational institutions, nowhere has the trend toward adult, part-time education been more pronounced than in the community colleges.

There courses range from principles of accounting to real estate to modern dance. At the Alexandria campus of Northern Virginia Community College, the winter catalogue lists 73 courses in auto ranging from principles of small gasoline engines to automotive air conditioning.

At Prince George's Community College, classes begin at 7 a.m. for students who want to get their courses out of the way before the workday starts. For those who don't have time to get to campus at all, there are classes on television.

Ten years ago, 52 percent of the students at Prince George's were 21 or under; now only 36 percent are.

Projections for the future vary, but few expect the boom in adult education to do anything but continue well into the 1980s.

"There must be a plateu somwhere, but I don't think we've reached it yet," says Betty Beall, an administrator of adult eduction at Georgetown. "This is definitely a growth industry. Lifelong learning is an idea that is catching on, and this is only the beginning."