William Edward Thomas, 18, who terrorized the prosperous Kalorama Triangle section of Northwest Washington last fall, was sentenced to serve a minimum of 37 years in prison yesterday after he earlier pleaded guilty to charges of armed rape, armed robbery and assault with intent to kill.

Thomas, who committed his first crime when he was 7 years old and who has been in and out of juvenile correction facilities since 1968, is a "nonfeeling, nonremorseful individual," said D.C. Superior Court Judge Eugene N. Hamilton before imposing sentence.

"It will take many years to tear away this callousness he has for other personss and restore him to some degree of understanding for other human beings," Hamilton said.

Federal prosecutors contended that Thomas was responsible for a rash of rapes, robberies, assaults and other offenses between September and December of last year in the Kalorama Triange and Adams Morgan areas.

Thomas lived at 2351 Champlain St, NW, on the edge of the areas where the crimes occurred.

Fear engulfed the neighborhoods, prompting residents and victims to band together to help the police with their investigation and circulate information about the crimes, eventually leading to Thomas' arrest.

Before yesterday's sentencing, Hamilton received numerous letters from citizens of the areas, who described their ordeal during those months and who asked that Hamilton impose a stiff sentence on Thomas.

"No one who lived through that terrifying period can ever forget it or ever feel truly safe again in the street," one citizen wrote to Hamilton.

"Surely no penalty imposed by society through its guardian, the court could ever compensate for the outrages against human dignity committed by William Thomas," one letter said.

Before Thomas was sentenced yesterday, one of his victims, a 37-year-old woman whom he raped, stabbed and shot twice, testified about the night she was assaulted. A 62-year-old woman, who the government said was another of Thomas' rape victims, sat in the courtroom along with several residents from the Adams Morgan-Kalorama Triange neighborhood.

Thomas was sentenced yesterday on three counts of armed rape, five of armed robbery and one count of assault with intent to kill. He pleaded guilty to the nine counts last April. Following yesterday's sentencing, Judge Hamilton granted a government motion to dismiss another 60 charges against Thomas.

Because of Thomas' age, Hamilton could have sentenced him under the Youth Corrections Act, which has as its maximum penalty an indeterminate sentence running up to 20 years.

However, after reviewing Thomas' juveline record, which included several instances where Thomas was sent to rehabilitative facilities for juveniles, Hamilton said he decided that the defendant would not benefit from further similar treatment. The judge then sentenced Thomas as an adult.

Hamilton recommended, however, that Thomas be committed to a federal prison, rather than the District's Lorton Reformatory. The judge also recommended that Thomas be given psychiatric therapy. The decision on where Thomas will be imprisoned will be made by the Bureau of prisons.

Thomas sat impassively through the court proceeding yesterday. When asked by Judge Hamilton if he had anything to say before he was sentenced, Thomas said:

"I know I can't take back the scars and bruises I put on the victims . . . but I would like to say I am sorry. There is nothing else I can say."

Before he sentenced Thomas, who was arrested 22 times as a juvenile, Hamilton noted that Thomas had been beaten and severely abused as a child. That background, Hamilton said, has "transformed this individual into something less than a human being."