HP stands for "Health Points" or "Hit Points" in some cases. In Lost Odyssey, HP represents a character's life force. Once a character's HP is depleted, they will either be knocked out (Immortals) or die (Mortals). If all characters in a selected squad have their HP reduced to 0, then the game is over. HP can be regained through the use of items such as Healing Medicine and Healing Tank, and characters that are skilled in the use of White Magic can also heal team-mates both during battle and from the main menu at the expense of their MP.
The Prayer ability heals a small amount of HP for no MP cost. Due to the low amount of HP restored, it is most useful near the beginning of the game, and becomes less effective as the game progresses.
An Immortal will have around 20% of their hit points returned after about three rounds after being knocked out. Mortals do not get any automatic restoration. Both Mortals and Immortals can be restored by the use of Revive, Resurrect or by items; however, this leaves the character low on HP and vulnerable to another attack until they are healed.