Expresses a tentative or speculative reason. Combines the causal connector -아/어서 with the copula 이다 and the wondering marker -ㄴ지. Used when suggesting a possible cause while acknowledging uncertainty.

• •Speculation: "피곤해서인지 자꾸 졸려요" (Perhaps because I'm tired, I keep feeling sleepy)
• •Tentative: "열심히 공부해서인지 좋은 성적을 받았어요" (Perhaps because I studied hard, I got good grades)