The quality or state of being bratty; spoiled, disobedient, or childishly obnoxious behavior.
From bratty plus the abstract noun suffix -ness, creating a noun that names the quality or condition itself rather than describing it.
Parents report that brattiness peaks around age 5-7, and child psychologists theorize this is when children first understand rules well enough to deliberately break them for attention—it's actually a sign of developing intelligence.
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