un·der·stand 
(ŭn′dər-stănd)
(ŭn′dər-stănd)v. un·der·stood (-std), un·der·stand·ing, un·der·stands
v.tr.
1.
a. To become aware of the nature and significance of; know or comprehend: She understands the difficulty involved.
b. To become aware of the intended meaning of (a person or remark, for example): We understand what they're saying; we just disagree with it. When he began describing his eccentric theories, we could no longer understand him.
c. To know and be tolerant or sympathetic toward: hoped that they would understand my complaint.
2. To know thoroughly by close contact or long experience with: That teacher understands children. I understand the basics of car repair.
3.
a. To learn indirectly or infer, as from hearsay: I understand his departure was unexpected. Am I to understand you are staying the night?
b. To assume to be or accept as agreed: It is understood that the fee will be $50.
4. To supply or add (words or a meaning, for example) mentally: A verb is understood at the end of the statement "Yes, let's."
v.intr.
1.
a. To have understanding, knowledge, or comprehension.
b. To have sympathy or tolerance: You're upset. I understand.
2. To learn something indirectly or secondhand; gather.
[Middle English understanden, from Old English understandan : under-, under- + standan, to stand; see stā- in the Appendix of Indo-European roots.]
Synonyms: understand, comprehend, apprehend, grasp
These verbs denote perception of the nature and significance of something. Understand is the most general and can apply to a range of situations or degrees of perception: understood the directions; understands only a little spoken Spanish; couldn't understand what I did wrong.
It can also refer to the thorough knowledge gained by close experience: "No one who has not had the responsibility can really understand what it is like to be President" (Harry S. Truman).
Comprehend stresses wide or thorough perception: "To comprehend is to know a thing as well as that thing can be known" (John Donne).
Apprehend denotes both mental and intuitive awareness: "Intelligence is quickness to apprehend" (Alfred North Whitehead).
To grasp is to seize an idea firmly: "We have grasped the mystery of the atom and rejected the Sermon on the Mount" (Omar N. Bradley).
These verbs denote perception of the nature and significance of something. Understand is the most general and can apply to a range of situations or degrees of perception: understood the directions; understands only a little spoken Spanish; couldn't understand what I did wrong.
It can also refer to the thorough knowledge gained by close experience: "No one who has not had the responsibility can really understand what it is like to be President" (Harry S. Truman).
Comprehend stresses wide or thorough perception: "To comprehend is to know a thing as well as that thing can be known" (John Donne).
Apprehend denotes both mental and intuitive awareness: "Intelligence is quickness to apprehend" (Alfred North Whitehead).
To grasp is to seize an idea firmly: "We have grasped the mystery of the atom and rejected the Sermon on the Mount" (Omar N. Bradley).