Definition and example to distinguish qualitative and quantitative research

I am looking for the best definition for qualitative and quantitative research. I wrote an article on UX Magazine in which I tried to address the need for doing research that tries to map what happens to why it happens.

I have seen articles use the term 'qualitative' and 'quantitative' research used to refer to these complementary types of research questions being asked. However, it seems that in the social sciences the terms refer to the type of methods (qualitative being associated with words and quantitative with numbers) rather the the type of question being asked (i.e. what happens as opposed to why it happens).

I wonder if UX practitioners have fully adopted the social science definitions combine both types of research methods in user experience studies. I think this is important because it is also possible to generate qualitative and quantitative data from qualitative or quantitative research methods.

My question is, what would be a UX practitioner's accepted definition of what qualitative and quantitative research is?

Does it necessarily have to fit with social science research, or can it be something different? Could we call it 'exploratory' and 'investigative' research instead?