One interesting note is that double negation in English was acceptable and used commonly until prescriptive grammarians wrote against it in the 18th century. For example Chaucer makes extensive use of double (and even triple) negatives in his writing. Today, double negatives are not considered "correct", especially for written English, but are somewhat accepted in spoken English, especially in humorous and informal usage. Double negatives are more extensively used in some dialects of English than in others.
According to what I have found, these are considered the negative words in English:
barely, hardly, neither, no, no one, nobody, none, not, nothing, nowhere, scarcely.