The relationship between 데, 는 데(에) and 는데(요) [UKG-011]

There is a relationship between 데 (place), 는 데에 (situation), 는데 (connective) and 는데(요) (sentence-final). In particular, 는 데에 (situation) and 는데 (connective) are ambiguously similar with a continuous boundary between them. The best way to understand these grammatical forms is to understand how they 'evolved' from 데 meaning 'place' and see how they are related.

See also:
[UKR-054] GRD entry for 는 데에:
https://ultimatekorean.com/ukr/054
[UKR-005] GRD entry for 는데(요):
https://ultimatekorean.com/ukr/005
[UKR-019] GRD entry for Grammaticalisation:
https://ultimatekorean.com/ukr/019
[UKG-006] An overview of 는데(요):
   • An overview of (으)ㄴ/는데 [UKG-006]  


References:
— Horie, K., & Sassa, Y. From Place to Space to Discourse: A Contrastive Linguistic Analysis of Japanese tokoru and Korean tey. (2001). Japanese/Korean Linguistics, 9, 181–194.

— Jang, Y., & Kim, H. The Synchronic and Diachronic Processes of Grammaticalization —- the Case of -tey and –nuntey. (2006). Harvard Studies in Korean Linguistics, 11, 438-451.

— Lee, H., & Park, Y. (1999). Discourse-pragmatics of the Korean connective -nûnte : a case of grammaticalization of figure-ground relation, presented at New Reflections on Grammaticalization: International Symposium, June 16-19, 1999. Potsdam, Germany.

— Rhee, S. (2017). Grammaticalization and Pragmatic Inference: The Case of Insubordination, presented at East Asian Special International Symposium: Pragmatics in East Asia; Its Practice & Contribution, December 16-17, 2017. Kyoto, Japan.