Charles Berlitz, 90, the eminent linguist who also wrote kooky and spooky bestsellers exploring the Bermuda Triangle, the lost continent of Atlantis and other paranormal activity, died Dec. 18 at a hospital in Tamarac, Fla. No cause of death was reported.

Mr. Berlitz was the grandson of Maximilian D. Berlitz, who founded the language schools that bear the family name. Charles grew up in a household where he was encouraged to learn a new language every year. By age 3, he spoke four languages and had created his own.

"I didn't realize they were speaking different languages," he told The Washington Post in a 1982 profile. "I thought every person had their own particular way of speaking. Since I'd hear my mother switch to German when she spoke to my grandfather, I thought everyone had to learn everyone else's way of speaking to communicate. I wanted my own language, too."

During his life, he was said to have learned everything from Arabic to Zulu. He wrote dozens of books about language, a subject he described as more than mere communication. Words also connote how cultures think, he said, citing as an example how the color red in China symbolizes joy, celebration and marriage, while white is associated with death and mourning.

His book "Native Tongues" (1982) was a compendium of anecdotes about the development of language. He noted that the Italian greeting "ciao" came from the word for "slave," schiavo, or "I am your slave."

Studying civilizations and his interest in underwater archaeology led to a successful, if much derided, career focused on the occult and other oddities.

In his bestseller "The Bermuda Triangle" (1974), he wrote about seemingly inexplicable disappearances of planes and ships in the Atlantic Ocean near Bermuda. A reviewer in Time magazine wrote: " 'Triangle' takes off from established facts, then proceeds to lace its theses with a hodgepodge of half-truths, unsubstantiated reports and unsubstantial science."

Nevertheless, the book sold an estimated 10 million copies and spurred Mr. Berlitz to write "Without a Trace" (1977), which included personal stories of people who claimed to have been affected by the Triangle. He also reported in the book the existence of a giant pyramid on the bottom of the ocean.

"I don't say all this stuff about the Bermuda Triangle is supernatural," he told an interviewer. "I just don't think we're at a point to understand it."

His other titles included "The Mystery of Atlantis (1969), "Mysteries From Forgotten Worlds" (1972) and "The Philadelphia Experiment: Project Invisibility" (1979), which alleged that the Navy had found a way to make matter invisible and hide its warships. A feature film was made of "The Philadelphia Experiment" in 1984.

Over the years, he also did counterintelligence and investigative work for the military.

He was born Charles Frambach in New York but changed his name to Frambach-Berlitz at his grandfather's request and later dropped Frambach altogether. He was a 1936 magna cum laude graduate of Yale University, where he was on the swim team.

He began working for the family language school during college breaks and became a company vice president, overseeing its New York-based publishing house. More than 28 million people bought its texts, which included tourist phrase books and pocket dictionaries.

Mr. Berlitz also played a key role in developing record and tape language courses and helped establish language courses for American businesses whose employees did work overseas.

He left the company in the late 1960s, not long after the publishing firm Crowell, Collier & Macmillan took over.

In a strange legal maneuver, the new owners obtained a temporary court order preventing Mr. Berlitz from using his surname professionally, arguing that Berlitz was a trademark. Mr. Berlitz laughed it off, telling the New York Times, "I am learning a rich new vocabulary of legal terms like 'injunction' and 'cross-motion,' which I expect to find very helpful for future translations."

By the mid-1970s, he had won the case and a settlement upward of $350,000. In the interim, he began his examinations of Atlantis and the Bermuda Triangle.

Survivors include his wife, Valerie Seary Berlitz, whom he married in 1950; a daughter; and two grandchildren.

He met his future wife when she was studying at a Berlitz school in Australia and asked for a refund. He said the encounter resulted in a marriage proposal but no money, explaining: "Hard company to get a refund from."

Charles Berlitz helped run his family's language school and publishing business.