An example of not used as an adverb is in the phrase "not happy," which means unhappy.
Origin of notMiddle English not, unstressed form of noht, nought, naught: see nought
Origin of notMiddle English, alteration of naught, nought; see naught. Usage Note: The positioning of not and other negatives in a sentence is important to avoid ambiguity. The sentence All classes are not open to enrollment could be taken to mean either “All classes are closed to enrollment” or “Not all classes are open to enrollment.” Similarly, the sentence Kim didn't sleep until noon could mean either “Kim went to sleep at noon” or “Kim got up before noon.” • Not only and but also are usually classified as correlative conjunctions. They add emphasis to each part of the construction and suggest that the second part is particularly unexpected or surprising. As with both &ellipsis; and and other correlatives, parallelism requires that each conjunction be followed by a construction of the same grammatical type. Thus, She not only bought a new car but also a new lawnmower displays faulty parallelism, where She bought not only a new car but also a new lawnmower does not, because both not only and but also are followed by noun phrases. See Usage Note at only.