Usually, plural English nouns are pretty straightforward. Just add an -s or -es, and you're done. However, there are more than a few odd ones out: words that change their vowels, acquire unexpected endings, or become almost unrecognizable. These irregular nouns are not random: they are linguistic leftovers from older forms of English and from the many languages that contributed to its vocabulary. Here's a list of 10 irregular plurals that are considerably more interesting than simply adding an -s.