The term 'life force' is a concept that has been around for centuries and is used to describe the energy that animates all living things. In crossword puzzles, the term is often represented by five different words: CHI (3 letters), LIBIDO (6 letters), MANA (4 letters), SPIRIT (6 letters), and PRANA (5 letters). CHI is an ancient Chinese concept of life energy, LIBIDO is a psychoanalytic term for sexual energy, MANA is a Polynesian term for spiritual power, SPIRIT is a term for the incorporeal essence of a living being, and PRANA is a Hindu term for life energy.