This thesis considers negation in 54 modern Arabic varieties from a typological point of view (as in Song 2001, Croft 2003 and Miestamo 2005). The types of negation investigated here are: standard negation, non-verbal negation, negative imperatives, negative existential clauses, negation with pseudo-verbs, negative indefinite pronouns and negative concord constructions. This approach results in 30 generalizations capturing different ways of expressing different types of negation among the contemporary varieties of Arabic; for example: the construction for standard negation in modern Arabic varieties is almost always symmetric (done by the addition of the negative morpheme to the affirmative clause only) and very rarely asymmetric (an example is the dialect of ʔAbha); there is no š-variety (a variety that uses ...-š negatively in standard negation) where ...-š is not, at least optionally, omitted in emphatic negation; the negator mā can commonly negate imperatives in every Arabic region, except in the Arabian Peninsula where this is extremely rare. One of the most interesting results the study reveals is that negation in Arabic is going through a cycle additional to the Jespersen’s cycle which is already identified by several studies (e.g., Lucas, 2009 and Diem, 2014). In the first stage of this additional cycle, a single negator is used to negate both verbal and non-verbal clauses. In the second stage, this negator is attached to a personal pronoun to negate non-verbal clauses only. In the third stage, a new single morpheme is coined and generalized to negate any non-verbal clause. In the fourth stage, this new morpheme is used to negate certain types of verbal clauses. In the last stage, verbal and non-verbal clauses return to be negated similarly, in that this new coined morpheme can negate both of them. In the study, this cycle is referred to as the Arabic negative cycle.