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Experience

Your level is determined by how many experience points you have.
Experience is gained through exploring, combat, and practice. You
can tell how much experience you need for your next level by
either using the attributes command or levels command. Experience
obtained is affected by a wide variety of things. For example,
players who are roleplaying will get a 15% experience bonus
for all experience gained. It is possible to lose experience
points by dying.

See also:
Roleplay, Level, Levels, Attributes, Kills, Combat,