Example: You don't need to explain--I understand!.
source: wordnet30
To have just and adequate ideas of; to apprehended the meaning or intention of; to have knowledge of; to comprehend; to know; as, to understand a problem in Euclid; to understand a proposition or a declaration; the court understands the advocate or his argument; to understand the sacred oracles; to understand a nod or a wink.(verb)
source: webster1913
To have the use of the intellectual faculties; to be an intelligent being.(verb)