A character having a lawful alignment.
"The knight's sword hummed with power because his heart remained firmly aligned to the lawful code of chivalry."
In plain English: A lawful is not actually a noun; it is an adjective that describes something allowed by official rules and regulations.
"The lawyer argued that his client had no lawful excuse for breaking the contract since he never signed it initially."
according to custom or rule or natural law
"The ancient king ruled as a lawful monarch because his authority was derived from divine right and established tradition rather than popular vote."
authorized, sanctioned by, or in accordance with law
"a legitimate government"
Conforming to, or recognised by the laws of society.
"The court ruled that the new agreement was lawful because it fully conformed to existing regulations."
In plain English: Lawful means something that is allowed by official rules and laws.
"The court ruled that his actions were lawful because he followed all local regulations."
Usage: Avoid using "lawful" when you simply mean legal; prefer "legal" in most contexts unless emphasizing conformity to specific rules rather than mere validity. In fantasy genres, reserve it for characters with an orderly or rule-abiding nature as defined by role-playing systems.
Lawful comes from the combination of "law" and "-ful," but its form was influenced by an older word meaning "according to law." This term entered English in Middle English with a clear sense of being permitted or valid under legal rules.