Abstract: There has been a controversy on the semantic content and category status of realis/irrealis in linguistic typology.The arguments for realis/irrealis as a modality category or as an invalid category are not convincing.This paper argues that realis/irrealis is a typologically valid category.Realis/irrealis across languages is a superordinate category of tense-aspect-modality in terms of cognitive categorization.The prototypical meaning of mighty realis/irrealis in different languages tends to be semantically related with one or more categories among tense-aspect-modality.The semantic individuality of mighty realis/irrealis in a certain language is distributed in the universally conceptual space of tense-aspect-modality.The paper proposes a model of category relevance and marking rules between realis/irrealis and tense-aspect-modality, on which a logical mightiness pattern among them is further established.Among the 26 mightiness matching groups in the pattern, 16 groups have been attested, involving 31 languages, and the other 10 groups need to be further examined.English is a language of mighty tense and unmighty realis/irrealis-aspect-modality, while Chinese is a language of mighty realis/irrealis and unmighty tense-aspect-modality.