​This study explores the realization of the complementizer ʔinnu in Ammani Arabic employing modern quantitative methods of the variationist approach. It examines the effect of some extra-linguistic and linguistic factors (age, gender, education, type of matrix, definiteness, specificity, word order, subject type and factivity) on the realization or omission of the complementizer in AA. The results reveal that the variable realization of the complementizer ʔinnu in AA is linguistically conditioned. The omission of the complementizer ʔinnu is subject to some linguistic constraints including the type of the preceding matrix and the word order of the embedded clause within ʔinnu. These factors play a statistically significant role in its realization/omission. Moreover, the results show that the social factors turned out to be statistically insignificant in constraining overt and null complementizer in AA. ​