Interested just means that I find something interesting. I want to know more about it, for any reason. Concerned means I am interested because I am worried about the topic. "I am concerned about your health." But, unlike the other words, neither "interested" nor "concerned" implies that you are doing anything. "attentive" implies you are paying attention to the needs of someone, and reacting. Eg: A nurse is attentive to her patient. If the patient calls for help, the nurse comes to help. And the nurse keeps track of the patient's temperature, blood pressure, etc, to make sure she know of problems when they come up. A good waitress is attentive - she notices when you are low on coffee and fills your cup before ou can ask. Solicitousness is an extreme form of attentiveness - like if the nurse came in to the patient's room every five minutes to ask if they are all right, if they want another pillow, etc. Someone who is "solicitous" can sometimes be annoying to the other person. Eg: Mr. Smithers on The SImpsons is solicitous of Mr. Burns. (he is also a lot of other things, such as obsequious (or, in slang, a suck up)) Someone who is "attentive" is never annoying; if they are annoying, they have become solicitous. "mindful" and "heedful" are very similar. They are like "attentive," but they are often used to imply that the person is NOT doing something (unlike "attentive," which usually isn't used that way). "John was mindful that Mary does not like large groups of people, so he did not buy her tickets to a concert for her birthday." "Heedful" is often used instead of "mindful" in the context of the other person saying something. "Heedful of Mary's statement that she does not like crowds, John did not buy her concert tickets." PS: Mindful is used much more often than heedful (mindful: 81,000,0000 hits on Google; heedful, 619,000)

Look them up on a dictionary.

oops i meant to answer, not comment. See my answer