LONDON - How do you sum up the work of songwriter Robert B. Sherman? Try one word: “Supercalifragilisticexpialidocious.’’

The tongue-twisting term, sung by magical nanny portrayers of Mary Poppins, is like much of Mr. Sherman’s work, complex and instantly memorable, for child and adult alike. Once heard, it was never forgotten.

Mr. Sherman, who died in London at age 86, was half of a sibling partnership that put songs into the mouths of nannies and Cockney chimney sweeps, jungle animals, and Parisian felines in films for Walt Disney and other studios.

Robert Sherman and his brother Richard composed scores for films including “The Jungle Book,’’ “The Aristocats,’’ “Mary Poppins,’’ and “Chitty Chitty Bang Bang.’’ They wrote the most-played tune on earth, “It’s a Small World (After All).’’

Mr. Sherman’s agent, Stella Richards, said Tuesday that he died in London on Monday.

His son, Jeffrey Sherman, paid tribute to his father on Facebook, saying he “wanted to bring happiness to the world and, unquestionably, he succeeded.’’

Jeffrey Sherman said in an interview that his father had learned the craft of songwriting from his own father, Tin Pan Alley composer Al Sherman.

“His rule in writing songs was keep it singable, simple, and sincere,’’ Jeffrey Sherman said. “In the simplest things, you find something universal.’’

Mr. Sherman knew another truth, his son said: “What seems so simple is really very complex. “He was a very simple guy, complex but simple. If you ever want to know about my Dad, listen to the lyrics of his songs.’’

Robert A. Iger, president and chief executive of the Walt Disney Co., said the company mourned the loss of “one of the world’s greatest songwriters and a true Disney legend.’’

Three Broadway marquees - including the New Amsterdam Theatre, where “Mary Poppins’’ is playing - were dimmed Tuesday night in Mr. Sherman’s honor.