watch attentively; "Please observe the reaction of these two chemicals"
discover or determine the existence, presence, or fact of; "She detected high levels of lead in her drinking water"; "We found traces of lead in the paint"
designate as if by a mark; "This sign marks the border"; "He indicated where the border ended"
be cognizant or aware of a fact or a specific piece of information; possess knowledge or information about; "I know that the President lied to the people"; "I want to know who is winning the game!"; "I know it's time"
know and comprehend the nature or meaning of; "She did not understand her husband"; "I understand what she means"
as in in botany or biology, for example
describe the qualities or peculiarities of; "You can characterize his behavior as that of an egotist"; "This poem can be characterized as a lament for a dead lover"
perceive by sight; "You have to be a good observer to see all the details"; "Can you see the bird in that tree?"