Specialization has spread to shopping center development.

Specialty centers can be strip centers, such as the Talbot Center along Rockville Pike, or malls, like Dodge Center in Georgetown. They may offer a movie theater or two, and ice cream parlor or a restaurant with a theme, and many are beginning to offer tennis and racquet ball clubs as space permits. But in general, the combination of stores is more appealing than any one shop.

These centers are found in metropolitan regions, often are accessible to tourist attractions and cater to shoppers whose income and lifestyle encourage "nonessential" spending, according to San Francisco sociologist Nina Gruen.

Specialty centers have been built in large population areas with few other "recreational shopping" opportunities; the centers are large or small, but generally do not have department stores. According to Gruen, who wrote about such centers in the January issue of the magazine, "Urban Land," they offer a mix of nonessential goods and services that attract consumers from a large market area.

Shopping centers fall into four major categories, according to their leasable space, the number of stores and types of tenants, adjacent residential population, location and total acreage. There are more than 200 centers of all kinds in the Washington metropolitan area.

The largest centers are the "super regional" ones that normally offer about 750,000 square feet of leasable space. They usually have at least three major department stores. In the Washington area, Tyson's Corner, Montgomery Mall, Landover Mall and Springfield Mall, among others, fall into this category.

Next in size are the "regional centers," which generally have 50 to 100 stores, at least one major department store and more than 300,000 square feet of gross leasable space. Such centers, like Seven Corners and Wheaton Plaza, often cover 35 or more acres.

"Community centers" house 20 to 40 stores and a junior department store and cover 100,000 to 300,000 square feet, followed by "neighborhood centers" with 10 to 15 stores, including supermarkets, drug stores, barber shops, cleaners and similar personal service retail outlets. They offer less than 100,000 square feet of gross leasable space and cover five to 10 acres.

All these centers are facing increasing competition from speciality theme centers such as Bethesda Square on Old Georgetown Road in Bethesda.

Bethesda Sqare has a carousel for small children, tennis courts, an ice cream parlor, two movie theaters, a plant store and a number of gift shops. And it owes some of its unusual design to the fact that it was converted from an old bowling alley.

The Urban Land Institute, an independent research and educational organization, says in its book, "Dollars and Cents of Shopping Centers - 1978," that specialty centers are the result of growth and competition in the shopping centers.

"Developers have begun to build and design centers which have characteristics different from those of traditional shopping centers," it was noted. By definition, each specialty center is different, although there are several similarities.

The mix of tenants is a primary factor in determining whether a center qualifies as a specialty one. According to the institute, specialty or theme centers have a unique tenant mix.

"These centers have a concentration of imported and gift specialty shops and specialty clothing, luggage and crafts and leather shops. They also have one or more restaurants and specialty food shops. Of particular note is the absence of general merchandise stores."

The architectural design is also a major feature of specialty centers. ULI notes that most of the specialty centers it studied have an unusual structural configuration. The average size, however, is only about 68,000 square feet, comparable to a neighborhood center although with a much different mix of tenants.

Specialty centers often feature theme restaurants that can serve as a draw for other retail shops in the complex, while super regionals normally have fast-foot restaurants to move customers out of the food, operation and into the retail outlets quickly.

Gruen noted that the typical shopping pattern for specialty centers is an initial visit for window shopping followed by a second visit to purchase something.

Craig Lussi, who along with his wife, Nancy, developed Bethesda Square, says this pattern holds true for many of his customers.

"People seem to enjoy coming in on a sightseeing tour, and then coming back another day to shop," Lussi said. "We're not a place where you have to shop, but where you want to shop for things you really don't need. We're not much bigger than a Giant food store, but we do offer a different kind of atmosphere."