Memento mori (Latin for 'remember that you [have to] die') is an artistic or symbolic trope acting as a reminder of the inevitability of death. The concept has its roots in the philosophers of classical antiquity and Christianity, and appeared in funerary art and architecture from the medieval period onwards. The most common motif is a skull, often accompanied by one or more bones. Often this alone is enough to evoke the trope, but other motifs such as a coffin, hourglass and wilting flowers signify the impermanence of human life. Often these function within a work whose main subject is something else, such as a portrait, but the vanitas is an artistic genre where the theme of death is the main subject. The Danse Macabre and Death personified with a scythe as the Grim Reaper are even more direct evocations of the trope. In English, the phrase is typically pronounced məˈmɛntoʊ_ˈmɔri, . It is reconstructed as ideally pronounced as something like mɛˈmɛntoː ˈmɔriː if spoken by an ancient Roman around the beginning of the AD era. Memento is the 2nd person singular active future imperative of meminī, 'to remember, to bear in mind', usually serving as a warning: "remember!" Morī is the present infinitive of the deponent verb morior 'to die'. Thus, the phrase literally translates as “thou shalt remember to die” but may be loosely rendered as "remember death" or "remember that you die". The philosopher Democritus trained himself by going into solitude and frequenting tombs. Plato's Phaedo, where the death of Socrates is recounted, introduces the idea that the proper practice of philosophy is "about nothing else but dying and being dead". The Stoics of classical antiquity were particularly prominent in their use of this discipline, and Seneca's letters are full of injunctions to meditate on death. The Stoic Epictetus told his students that when kissing their child, brother, or friend, they should remind themselves that they are mortal, curbing their pleasure, as do "those who stand behind men in their triumphs and remind them that they are mortal".