Apprehend and comprehend mean to lay hold of something with the mind so as to know it but together with their derivative nouns apprehension and comprehension are clearly distinguished in psychological use.
Apprehend and apprehension do not imply attainment of full knowledge or of complete understanding but only a glimpsing of the nature, meaning, or significance of the object of thought; comprehend and comprehension imply an understanding of the object of thought in its entire compass and extent. (see also: Understand vs Comprehend vs Appreciate and Include vs Comprehend vs Embrace vs Involve vs Imply vs Subsume)
- The infinite distances of space are too great for the human mind to comprehend.
- She could not comprehend how someone would risk people's lives in that way.
Apprehend may suggest a single act of the mind and comprehend a complex and laborious process, but this distinction is not so essential as that between imperfect and perfect understanding; thus, one apprehends many things (as infinity or beauty) which one can never comprehend; one apprehends many things as a child (as mother love) which one does not comprehend until late in life. (see also: Arrest vs Apprehend vs Attach vs Detain and Foresee vs Foreknow vs Divine vs Apprehend vs Anticipate)