comprehension - understanding
Both comprehension and understanding can be used to talk about someone's ability to understand something.
He noted Bond's apparent lack of comprehension.
The problems of solar navigation seem beyond comprehension.
A very narrow subject would have become too highly technical for general understanding.
If you have an understanding of something, you have some knowledge of it, or you know how it works or what it means.
The past decade has seen huge advances in our general understanding of how the ear works.
The job requires an understanding of Spanish.
You cannot use comprehension with this meaning.
Understanding has another meaning. If there is understanding between people, they are friendly towards each other and trust each other.
What we need is greater understanding between management and workers.