Kas tu esi?

The Lithuanian phrase 'Kas tu esi?' translates directly to 'Who are you?' in English. Let's break down the etymology of each word: * **Kas (Who/What):** This interrogative pronoun has deep roots in Proto-Indo-European (PIE). It derives from the PIE root *kʷos, which was used to form interrogative and relative pronouns. This root is incredibly ancient and has cognates across many Indo-European languages. For instance, it's related to the Latin 'quis' (who), Sanskrit 'kaḥ' (who), Old English 'hwā' (who, from which modern English 'who' evolved), Russian 'kto' (кто - who), and Greek 'tis' (who). In Baltic languages, this PIE root evolved into forms like Old Prussian 'kas', Latvian 'kas', and ultimately Lithuanian 'kas'. Over millennia, its core function as an interrogative pronoun for identity or nature has remained consistent. * **tu (you - singular informal):** This personal pronoun also traces back to a very old PIE root: *tu-. This root signifies the second-person singular pronoun. We can see its descendants in a vast array of Indo-European languages, indicating its fundamental role in communication. Examples include Latin 'tu', Sanskrit 'tvam', Old English 'þū' (from which archaic English 'thou' comes), German 'du', Russian 'ty' (ты), and Greek 'sy' (σύ). In the Baltic branch, it developed into Old Prussian 'tu', Latvian 'tu', and of course, Lithuanian 'tu'. The form has been remarkably stable, preserving its core meaning of addressing a single person informally. * **esi (are - 2nd person singular present tense of 'to be'):** The verb 'esi' comes from the infinitive 'būti' (to be). The root for 'to be' in Indo-European languages is notoriously complex, often involving a merger of two distinct PIE roots: *bʰuH- (to become, grow) and *h₁es- (to be, exist). Lithuanian 'esi' primarily derives from the *h₁es- root, which is responsible for the 'is', 'am', 'are' forms in many languages. This *h₁es- root is found in Latin 'es' (you are), Sanskrit 'asi' (you are), Old English 'eart' (you are), German 'bist' (are - though 'bist' combines elements of both roots), and Russian 'est'' (есть - is, from which the modern 'ty yest'' is implied rather than explicitly stated). The Lithuanian 'esi' (you are) is a direct descendant of this ancient *h₁es- root, showing the characteristic Baltic sound changes. It maintains the essential meaning of existence or state for the second person singular.