1) A formalized idea or set of principles that attempts to define and explain a phenomenon is called .

Theory

Explanation:

Theory -

It refers to the type of process , which helps to define the phenomenon of any activity , experiment or study , is referred to as a theory .

The theory gives the complete , brief information and the numerical data about the given process , in a very explainatary manner .

Hence , from the given statement of the question ,

The correct term is theory .