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False positive:

In analytical Chemistry, False positive is an assumption that the concentration of analyte goes above a certain limit, in fact the concentration is below the limit.

False negative:

In analytical Chemistry, False negative is an assumption that the concentration of analyte is lower than a certain limit. In fact, the concentration is above the limit.

When you get a positive test result when you should have gotten a negative result, it's known as a false positive. It's also known as a "false positive error" or "false alarm." It's most commonly employed in the medical area, but it can be applied to other fields as well (like software testing).

Examples:

• A pregnancy test indicates that you are pregnant when you are not.
• You have a positive cancer screening test, but you don't have the disease.
• A prenatal test for Down's Syndrome comes up positive even though your foetus does not have the disorder.
• Your computer's virus software wrongly classifies a safe programme as harmful.

When a negative test result is incorrect, it is referred to as a false negative.To put it another way, you get a negative test result when you should have had a positive one. For instance, suppose you take a pregnancy test and it comes back negative (not pregnant). You are, however, expecting a child. It's possible that you got a false negative on a pregnancy test because you took it too soon, used diluted urine, or checked the findings too quickly. A false negative is a possibility with almost every diagnostic test. A cancer test, for example, could come back negative when you truly have the condition.