What is the difference among the three terms "research study", "research" and "study"?, please help me!, thanks in advance!
I'd say sometimes they're interchangeable, depending on the context. Below is the common definition of each term:
Study refers to a single paper or project, for example: This study showed that massage was effective in reducing stress. ← this paper states that massage was effective in reducing stress
Research includes a whole process of performing research: you look deeper into a topic by investigating the topic with different methods, including collecting data, performing trial(s)/experiment(s), and/or reading studies conducted by others... etc. in order to establish facts and reach new conclusions. For example: Avoiding bias is important when conducting research.
Research study is a scientific study on a particular topic which includes the process of research and new research results. A study purely based on existing materials without presenting new conclusions will not be called a research study (for example: literature reviews).