The title of this article may be quite confusing. You may wonder why we are asking the same question twice. However, if you look closely, you will see that there are three words in the title that are spelled in two different ways—“cancelled/canceled,” “marvellous/marvelous,” and “travelling/traveling.”
In all three cases, both the spellings are correct depending on the type of English being used—American or British. American English is notorious for shortening the length of words; thus, it is apparent that the spelling that uses the single l belongs to the American style of writing English and the ll spelling is a British one.
However, the above rule does not apply to all such words. For example, the term “patrolling” will always be spelt with ll, no matter the English type. This is because the l or ll rule depends on the positioning of vowels and consonants as well as the position of the syllable that is stressed upon while pronouncing the word.
In American English, when a multi-syllable word ends with a vowel followed by a consonant—which is the case for the three words mentioned in the title—the consonant is doubled when adding a suffix only if the stress is on the final syllable while pronouncing the word. For example, in the word “expel”, the stress is on the final syllable (ex∙PEL); therefore, the consonant is doubled when a suffix is added to it. Thus, the American English spelling of the word will also be spelled with ll like its British counterpart, i.e., expelling. However, in the word cancel, the stress falls on the first syllable (CAN∙cel); therefore, contrary to its British English counterpart, only a single l is used in its spelling when it is followed by a suffix, i.e., canceling.
The rules that govern the different spellings for the same word in their British English and American English counterparts were first elucidated by Noah Webster, an American lexicographer, textbook pioneer, English-language spelling reformer, political writer, editor, and author. He was one of the creators of the Merriam‒Webster dictionary. Webster greatly influenced the popularization of American English spellings as he included the shorter versions of words which had multiple spellings in his dictionaries, and gradually it was these shortened versions which became popular in the United States.
Other English-speaking countries and continents like Canada and Australia, and even previously colonized countries like India, still prefer the British version of most English words in their writing, although American spellings are quickly catching up worldwide.