Between listen and hear is a difference like that between the words look and see. (Compare synonyms for LOOK.) To hear is simply to become conscious of sound, to listen is to make a conscious effort or endeavor to hear. We may hear without listening, as words suddenly uttered in an adjoining room; or we may listen without hearing, as to a distant speaker. In listening the ear is intent upon the sound; in attending the mind is intent upon the thought, tho listening implies some attention to the meaning or import of the sound. To heed is not only to attend, but to remember and observe. Harken is nearly obsolete.