The word 坦诚 is formed by combining two characters, each contributing a core concept to create a new, unified idea. The first character, 坦, evokes the image of a flat, open expanse of land, suggesting a quality of being level, open, and without obstruction. The second, 诚, represents sincerity, honesty, and truthfulness in one's heart and speech. When fused, they metaphorically paint a picture of one's inner thoughts and feelings being laid out as plainly and openly as a flat, unobstructed plain, thus forming the compound meaning of "frank and open-hearted", where sincerity is presented without barriers or hidden corners.