Granny flats, shared housing, group homes, accessory apartments, mother-in-law flats, kangaroo apartments, reverse-annuity mortgages -the new lingo is confusing, but the force behind it quite simple. America's ranks of the elderly, up 25 percent in the 1970s alone, are continuing to rise rapidly. So are their housing needs.

The good news is that a new generation of housing solutions for older Americans -experimental ideas, many quite promising--is cropping up across the land. All are based on local initiative, not national policy.

The last national policy for housing elderly Americans--coaxing them out of their homes and neighborhoods and into sterile government-subsidized high-rise structures -is doubly discredited. First, federal-subsidy money is drying up, perhaps never to return. Second, surveys show that the elderly, in overwhelming numbers, don't want to move. They'd prefer to "age in place," if not in their own homes, then at least in their old neighborhoods with the friends, stores, parks and places they've known for years.

Shared housing and group homes are two of the most popular ideas. In shared housing, an older person invites one or more other persons--sometimes other elderly, sometimes younger people, and oftentimes both--to share his or her larger house.

Group homes, a slight variant, involve several elderly persons living together in a house none of them owns, often with a salaried resident professional.

The basic concept, writes Phyllis Myers in a forthcoming Conservation Foundation publication on "The Elderly in Revitalizing Neighborhoods," is "an attempt to recreate, in modern communities, the type of living experienced in societies with extendes families, where aging and younger persons helped each other.Preactical benefits include shared housing costs, lessened fears of crime, companionship and assistance with household chores."

For elderly people buffeted by high rentals and inflation, such arrangements can be an economic godsend. For communities with shortages of affordable rentals, the housing supply is increased.

Matching services, linking people offering space in their homes with those seeking shelter, are springing up all across the country. Some clients pay rent; younger people sometimes barter their help in the home for free room, and occasionally free board.

Making compatible matches isn't always easy, says Leah Dobkin of Homesharing for Seniors in Seattle. Among the factors are desired location, costs, space requirements, kitchen, arrangements, sex, smoking, drinking, pets, "and above all, attitudes, values, interests and personality factors." Still, the benefits can very real. "It's worth an awful lot to get a good night's sleep because there's another person in the house," says one "matched" elderly person in Duluth.

Short of actual shared housing, thre's the accessory apartment, or as many call them, "family conversions," "mother-in-law apartments," "mother-daughter homes." In Denmark they're called "kangaroo apartments." All the terms refer to an independent unit -converted garage or reckroom, back wing, upper floor or whatever -added onto or carved ot of a single-family house.

The potential benefits for everybody are impressive, notes housing consultant Patrick Hare: Older homeowners receive rental income and often are enabled to stay in homes they'd otherwise have to leave; both young and old apartment-seekers can find inexpensive rentals; the elderly have reduced fears of criminal instrusion or personal accidents when alone.

The rub is zoning: accessory apartments are illegal in most singlefamily home neighborhoods. Proposals to legalize them raise fears about "changing the character of our neighborhood." There's an economic issue, too, since ownership has usually paid off financially beyond homeowners' fondest expectations. "Tinkering with single-family zoning means tinkering with the underpinnings of the 'good life' many people worked so hard to achieve," says Hare. But legal or not, the accessory apartments are coming, in city and suburb alike. Long Island has an estimated 15,000, and they're appearing increasingly throughout the country.

Then there's the "granny flat" -an idea born in Australia and first publicized here by the Council on International Urban Liaison. The idea is to put a small, removable cottage in a back or side yard to let one's elderaly parent live morr idependently, but still close to son or daughter. The first U.S. prototype is in Lancaster, Pa., where the local Amish seek to preserve extended family living.

Right now, most zoning laws prohibit granny flats (or, as some call them, "echo housing"). They're not, like accessory apartments, easily hidden. But communities may consider them much more seriously, Myers suggests, as the costs of housing and nursing homes soar.

The alternative to new housing opportunities for the elderly are grim: driving more into nursing homes, where many quickly become frail and dependent, at a huge cost to them and to the government through Medicare and Medicaid. How much better it seems to permit older people to "age in place," in familiar surroundings, as long as possible. Such supportive services as meals-on-wheels, community senior centers, anti-crime patrols, health check-ups, special transportation and daily telephone reassurances cost a fraction of institutionalization.

The Conservation Foundation's survey turned up a whole range of ways that elderly homeowners--80 percent of whom are women -can be given a hand in keeping their own homes. Local governments, sometimes using federal community-block grants, often do help the elderly poor overcome seeminly insurmountable barriers in financing home repairs or weatherization to reduce escalating energy costs.

Now being introduced, though at a painfully slow pace, are ways elderly people can stay in their homes but benefit from the equity locked up in their houses. One idea is a "reverse-annuity mortgage" in which a bank gains eventual title to the house but gives the homeowners monthly payments to cover living expenses.

Whether in cities, which have disproportionate numbers of older people, or in the suburbs, where most people now approaching 65 live, helping the elderly continue active, independent lives in their own neighborhoods should be everyone's goal. The elderly are us. We--if not now, then in time--are they.