What word in English does the following: becomes plural by adding an S in the middle?

English, with its rich history and diverse linguistic influences, offers many fascinating quirks, particularly when it comes to forming plurals. While most nouns simply add an 's' or 'es' to the end, some words defy this convention in unique ways. One such intriguing example involves a word that inserts the pluralizing 's' not at its conclusion, but directly into its middle.

Consider the term for a male royal heir, which, when referring to more than one, adds an 's' between the 'c' and the 'e'. This unusual formation transforms the singular into its plural form by essentially tucking the 's' into the word's interior. This method of pluralization, while rare in modern English, highlights the historical evolution of the language and its borrowing from other tongues, where such internal changes were more common. It serves as a delightful example of how words can retain vestiges of older grammatical rules.

The word itself, derived from the Old French "prince" and ultimately from the Latin "princeps," meaning "first" or "chief," carries a long lineage of noble connotations. Its plural form, "princes," maintains a connection to its Latin root, where similar internal inflections were a feature of word construction. This particular pluralization method, sometimes referred to as an "intercalated s," makes it a standout among English nouns. It’s a subtle but interesting reminder of the dynamic and sometimes unpredictable nature of English grammar, offering a small glimpse into the historical layers that shape our everyday vocabulary.