I've written in the past about native Chinese speakers confusing singular and plural nouns: adding an "s" to the end of a noun when it doesn't belong there, leaving the "s" off when it should be used. Adding an "s" is the most common way to make a singular noun into a plural, but because the English we know today has evolved from so many other languages – German, French, Latin and Greek – there are many so-called "loan" words in English that take unusual plural forms. These add to the confusion of people trying to learn the language, but even native English speakers often get them wrong.