To found or root something on a particular idea or occurrence. A noun or pronoun can be used between "base" and "on" or "upon." My love of science is based upon an interest in experimentation. Unfortunately, she has a low opinion of me. I think she based it on our first meeting, which didn't go well.
See also: base
base something (up)on someone or something
to ground something, such as one's opinion, decision, or thinking, on someone or something; to found one's ideas or attitude on something. (Upon is more formal and less commonly used than on.) I base my opinion on many, many facts. I based my opinion upon my own seasoned judgment.
To form, develop, or found something on the basis of something else: I based my decision on the information you gave me. The film was based on a popular book.