One of the three lower realms of existence (Skt. durgati, apāya). Unlike the modern biological classification of life in which humans are classed along with animals, Buddhism in ancient Asia developed its own taxonomic system that divided forms of sentient life (plants excluded) into six (or sometimes five) realms of existence or rebirth destinies (Skt. gati): gods (Skt. deva), demigods (Skt. asura), humans (Skt. manuṣya), animals (Skt. tiryak), hell beings (Skt. naraka), and ghosts (Skt. preta).