When did you last say to someone that you had a headache? Did the listener understand what you meant? If you now reply "yes", how do you know that? Perhaps she usually means by the term "headache" something different than you do. How can we find out whether or not this assumption is true?When did you last say that someone, for example, a patient or a relative, had jaundice? Did you mean that her skin and the whites of her eyes looked yellow? Do you say "yellow"? What does this term mean? Try to explain it to me and to yourself. After having explained it, consider the following, additional question. Under what light condition did you look at her skin and the whites of her eyes? Try to look at them under another light condition and to describe what you see then.