negligence

Short definition from Wiktionary

Noun

1. 1
   The state of being negligent.
2. 2
   The tort whereby a duty of reasonable care was breached, causing damage: any conduct short of intentional or reckless action that falls below the legal standard for preventing unreasonable injury.
3. 3
   The breach of a duty of care: the failure to exercise a standard of care that a reasonable person would have in a similar situation.