Muses (sacred poetry) is often seen with a pensive expression; Terpsichore (choral dance and song) is often seen dancing and carrying a lyre; Thalia (comedy) is often seen with a comic mask; and Urania (astronomy) carries a pair of compasses and the celestial globe. Greek "mousa" is a common noun as well as a type of goddess: it literally means "art" or "poetry". According to Pindar, to "carry a "mousa"" is "to excel in the arts". The word derives from the Indo-European root "men-", which is also the source of Greek "Mnemosyne" and "mania", English "mind", "mental" and "monitor", Sanskrit "mantra"
Muses and Avestan "Mazda". The Muses, therefore, were both the embodiments and sponsors of performed metrical speech: "mousike" (whence the English term "music") was just "one of the arts of the Muses". Others included Science, Geography, Mathematics, Philosophy, and especially Art, Drama, and inspiration. In the archaic period, before the widespread availability of books (scrolls), this included nearly all of learning. The first Greek book on astronomy, by Thales, took the form of dactylic hexameters, as did many works of pre-Socratic philosophy. Both Plato and the Pythagoreans explicitly included philosophy as a sub-species of "mousike". The "Histories" of Herodotus, whose primary