A grammatico-pragmatic analysis of the  because X construction: Private expression within public expression

Background: This article investigates an innovative use of  because, called the  because X construction (e.g., because homework). Quantitative and qualitative research as well as research about the historical development of the construction have been conducted. The present article aims to determine what motivates the use of the construction.  Methods: Based on the data collected from the literature and online sources, the grammar of the  because X construction is described in detail. The construction is then analyzed  within Hirose's (2015) three-tier model of language use.  Results: A two-layered expressive structure is proposed: The X-element serves as a private expression, which is a speaker's expression of thought with no intention of communication, whereas the whole construction functions publicly. The private nature of the X-element consistently accounts for the syntactic categories of the X-element and the restrictions on them observed in the literature.  Conclusion: The proposed two-layered expressive structure reflects a metapragmatic function of the construction. A private, subjective expression embedded in a public expression has the function of connecting the hearer to the speaker, and it accordingly brings about a joint attention effect. With such a function, the proposed structure is effective especially (but not exclusively) in online communication because one can strategically indicate closeness or intimacy to others, particularly in an environment where nonverbal means are difficult to apply.