[{"Bold_text": "adjective", "List Items": ["very slight, gradual, or subtle:the imperceptible slope of the road.", "not perceptible; not perceived by or affecting the senses.Synonyms: undetectable , unperceivable , hidden"]}, {"Bold_text": "noun", "List Items": ["something not capable of being perceived by the senses:metaphysical speculation about imperceptibles."]}]