ars

Ars, artis, f., third declension i-stem, so the genitive plural is artium and the ablative singular arte. The nominative hides the stem: art- plus s, with the t swallowed in the spelling.

The meaning is wider and drier than English "art". An ars is any body of teachable technique, so medicine, rhetoric, generalship and shoemaking are all artes; the artes liberales are the seven subjects fit for a free man, which is where the modern arts degree comes from. Cicero's ars is method; the gallery sense arrives much later. It also turns sour easily, so artes in the plural can be tricks or wiles, and artificium slides the same way. The family gives artifex, "craftsman", inertia (in- plus ars, want of skill) and English artisan, artifice and artful.