「深い」(ふかい) describes something that extends far down from the surface, like a deep well or a deep sea. It can also refer to something profound or intense, such as a deep understanding or a deep color, or a deep relationship. It implies a significant degree or extent in various contexts. Example: この海の底はとても深いです。 (The bottom of this sea is very deep.)

表面から底までの距離があること。また、程度が強いこと。