adjective
BAD : There was a negligent amount of liquid in the test tube.
GOOD : There was a negligible amount of liquid in the test tube.
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negligent = failing to take proper care, especially in your job; careless: 'The court decided that the pilot of the crashed aircraft had been negligent.'
negligible = (of an amount) so small that it has no effect and can be ignored: 'The cost of maintaining the machine is negligible.'