The quality or state of being deep in space, knowledge, emotion, or intensity.
From 'deep' + '-ness' suffix (a Germanic suffix creating abstract nouns). This formation is ancient in English and appears in Old English texts.
The 'deepness' of the ocean versus the 'deepness' of thought are measured by completely different scales, yet we use the same word—showing how language stretches metaphorically.
Complete word intelligence in one call. Free tier — 50 lookups/day.