Warning (noun)

1. An act of giving notice or warning of danger or harm.
2. A statement or message that advises or cautions someone.
3. An indication or sign that something is likely to happen.

Origin:

Middle english warnynge, from old english war(n)ung; akin to old high german warnung warning, latin vigilare to keep watch.

Examples:

1. He ignored the warning signs and drove into the flood.
2. The company issued a warning to its employees about the fraud.
3. The storm warning was issued for the entire coast.
4. The teacher gave a warning to the students about plagiarism.
5. The warning alarm went off when the gas leaked.