Respawn Time

Category:Terminology
Generally, the amount of time (usually between a minimum and maximum value) in which an enemy will spawn again after being defeated. Usually refers to Notorious Monsters.
Standard enemies will generally have a respawn time of 5 minutes in outdoor areas and 16 minutes in dungeon areas (Earth time). This is only a rough guideline and there are exceptions.
Notorious Monsters, in addition to the respawn time, tend to require additional conditions to get them to appear:
*In Lottery Spawn situations, use of this term refers to the point in time at which a "placeholder" enemy, usually a standard monster, may be defeated for a chance to cause a different enemy, usually a NM, to spawn in its place. This window remains open until the NM is spawned and defeated. If the placeholder is never defeated, the NM can never spawn.
:(Example: Valkurm Emperor
*In Timed Spawn situations, use of this term refers to the window of time in which the enemy will respawn on its own, without needing to defeat a placeholder. Although these enemies respawn in a similar fashion to normal enemies, NMs tend to take much longer to respawn than standard monsters do. 
:(Example: Shikigami Weapon)
*In Forced Spawn situations, use of this term refers to the window of time in which the target for spawning an enemy will be available again, if applicable. Most forced spawns become available again 15 minutes (Earth time) after the spawned enemy is defeated or despawns (after defeating the party that spawned it); others become available again immediately, meaning they have no respawn time. Forced spawns tend to require an item to be traded to a certain point (usually a ??? point) to make the NM appear.
:(Example: Morion Worm)
*Some enemies require additional special conditions that must be fulfilled before they can respawn, even if the respawn time requirement has been met. Common special spawn conditions include time of day (Vana'diel time), or a certain weather effect. If such a condition ends and the enemy is not currently aggressive toward any player or party (generally meaning it's unclaimed), the enemy might despawn, and will not respawn until the condition is met again. In certain cases, the NM might be considered as "defeated" in this circumstance and it may be necessary to wait the full respawn time before it can appear again.
:(Example: Kreutzet)
Knowing a NM's method of respawn, combined with its Time of Death, a rough estimate can be made of when the enemy can/will respawn following its defeat. This allows players to plan ahead and "camp" NMs only during the times when they are actually capable of appearing.