com·pre·hen·sion 
/ˌkɑ:mprɪˈhɛnʃən/ noun
/ˌkɑ:mprɪˈhɛnʃən/ noun : ability to understand [noncount] ▪ He has not the slightest comprehension of the subject. [=he does not understand the subject at all] ▪ The students showed excellent reading/language comprehension. ▪ The war caused suffering beyond comprehension. [=suffering that is impossible to imagine] ▪ mysteries that are beyond our comprehension [=mysteries that we cannot understand] [singular] ▪ I don't have a clear comprehension [=understanding] of how it works.
