Mental process of a person who comprehends; Comprehension usually used with of. He noted bond's apparent lack of.
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Both comprehension and understanding can be used to talk about someone's ability to understand something. The meaning of understanding is a mental grasp : Knowledge about a subject, situation, etc.
Or about how something works:
Understanding is a relation between the knower and an object of understanding. How to use understanding in a sentence. Understanding implies abilities and dispositions with respect to an object.