(1):

(n.) The quality or state of being negligent; lack of due diligence or care; omission of duty; habitual neglect; heedlessness.

(2):

(n.) An act or instance of negligence or carelessness.

(3):

(n.) The omission of the care usual under the circumstances, being convertible with the Roman culpa. A specialist is bound to higher skill and diligence in his specialty than one who is not a specialist, and liability for negligence varies acordingly.