The phrase "know well" expresses a level of familiarity and understanding that goes deeper than just being familiar with something. Some synonyms for "know well" include being acquainted with, being familiar with, being conversant with, being versed in, being knowledgeable about, and being experienced in. These phrases each offer a slightly different shade of meaning, but all convey a level of understanding that goes beyond surface-level knowledge. Whether it's a subject, a person, or a place, knowing it well implies a depth of recognition that comes from experience and engagement. By exploring different ways of expressing this idea, we can find the words that best capture our unique understanding of the things that matter most to us.