The extent to which the text as a whole is easy to understand. That is, the extent to which valid information and inferences can be drawn from different parts of the same document.
Comprehensibility reflects the degree to which a complete translation can be understood (whereas intelligibility is based on the general clarity of the translation, whether this is considered in its entirety or by segments out of context). (Halliday in Van Slype's Critical Report).
Subjective evaluation of the degree of comprehensibility and clarity of the translation. (Van Slype in Van Slype's Critical Report).
Halliday (in Van Slype's Critical Report): Noise test
Leavitt (in Van Slype's Critical Report): Multiple-choice questionnaire.
Orr (in Van Slype's Critical Report): Multiple-choice questionnaire.
Sinaiko (in Van Slype's Critical Report): Knowledge test.
This has also been called comprehension or intelligibility.
Metrics bearing on the readability of single sentences, as opposed to the comprehensibility of the text as a whole, have been moved to the Readability feature (2.2.1.1.1.1/172)