Sentence:  The drama in the theater and the concert in the hall both have a fixed time , but the time is fixed by the director and the players , the conductor and the instrumentalists , subject , therefore , to much variation , as record collectors well <WSD>know</WSD> . 
Meaning of the word marked with <WSD> tags:  be cognizant or aware of a fact or a specific piece of information; possess knowledge or information about