olemus
Wiktionary:
1. (uncountable, countable in some dialects) diligent inquiry or examination to seek or revise facts, principles, theories, applications, etc.; laborious or continued search after truth
2. (countable, dated) a particular instance or piece of research

ülevaateid
https://en.wikipedia.org/wiki/Research

https://www.discoverphds.com/blog/types-of-research

https://www.educba.com/types-of-research-methodology/

https://www.scribbr.com/methodology/types-of-research/

https://innspub.net/types-of-scientific-research/

https://eduvoice.in/types-research-methodology/