Tip: See my guide to the Most Common Pronunciation Errors in English. It will teach you about commonly mispronounced words, pro­nunci­ation patterns, and the basics of English phonology.

In French, Italian, German and some other languages that use the Latin alphabet, the spelling difference between “s” and “ss” is used to indicate a difference in pronunciation, namely between /s/ and /z/. More precisely, in certain positions (between two vowels, for example), “s” is pronounced as /z/ in many languages. If the given word is indeed to be pronounced with an /s/, the spelling changes to “ss”.

This rule has partially disappeared in English—there are many words now in which “s” is pronounced as /s/ even in positions in which it would be pronounced as /z/ in most other languages. But it still holds the other way round: “ss” in English is virtually always pronounced as /s/.

For this reason, English learners often tend to pronounce “ss” invariably as /s/, but this is not always the right pronunciation. Nonetheless, the number of exceptions is so low that we can easily list them all here (and some of them are quite common words). Here they are: