A more thorough explanation:

negative, adj.

1. Of or relating to something bad; not positive. Example: "She has a negative attitude towards her job."
2. Of or relating to refusal of consent; not affirmative. Example: "The boss gave a negative answer to the proposal."

negative, n.

1. A word or phrase of denial or refusal. Example: "No" and "not" are negatives.
2. A word expressing the opposite of the positive. Example: "I don't have any money" is a negative statement.
3. The original plate of a photograph, on which light and shadows are the opposite of the positive images later created and printed. Example: "The photographer asked for the negatives to be returned so he could make prints."
4. Archaic. The power of veto. Example: "The king's negative has eroded over time."

negative, vb.

To negate; to deny, nullify, or render ineffective. Example: "The jury negatived fraud."

In simple terms, negative means something bad or the opposite of something positive. For example, a negative attitude is a bad attitude, and a negative answer is a refusal to give consent. A negative word or phrase is one that denies or refuses something, like "no" or "not." In photography, a negative is the original image that is the opposite of the final print. To negative something means to deny or nullify it, like when a jury negatived fraud.