Do You Spell It “Buses” Or “Busses”?

The short answer: both buses and busses are acceptable plural forms of bus. However, buses is much more commonly used—almost exclusively—and is often considered the standard form.

The explanation: in many cases in English spelling, final consonants like the s in bus are often doubled when an ending such as -es, -ed, or -ing is added to the end of the word. For example, the word nag becomes nagged in the past tense. This spelling—with a double consonant—makes it clear the word should be pronounced with a short vowel sound. Otherwise, it may seem as though the word should be pronounced with a long vowel sound as it is in words with a silent -e that follows a consonant (like cave, kite, and rope).

For example, doubling the t in dot when spelling dotted avoids it being confused with the word doted. Since buse isn’t a common word that may confuse things, we usually just pluralize bus as buses. The same applies to gases. Relatedly, when bus is used as a verb (meaning “to transport by bus” or “to clear tables at a restaurant”), it can take the forms buses/busing/bused or busses/bussing/bussed. In this case, these forms are used with just about the same frequency—in bus, doubling the s when changing the verb tense is much more common than it is for the purpose of pluralization.

The (very abbreviated) history: anyone learning how to spell words in English knows just how frustrating it can be, but many of the “rules” have long historical precedent. The practice of doubling consonants goes back to the earliest days of English, and was often done to distinguish vowel length (that is, to make it more obvious whether a vowel should be pronounced short or long) in words with very similar forms. That said, plurals like buses and gases are exceptions.