The antonyms for the word "un-concern" are many and varied. These include concern, care, interest, involvement, attention, and consideration. When we are concerned about something, we take an active interest in it, and we pay attention to the details. Similarly, when we care about someone or something, we take a personal interest in their well-being and pay close attention to their needs. On the other hand, when we show interest, we demonstrate a desire to know more about something or someone. And when we get involved in something, we take an active role and give it our full attention. Finally, when we show consideration, we demonstrate awareness of other people's needs and feelings.