The quality or state of being erratic; the tendency to behave unpredictably or inconsistently.
Formed from 'erratic' plus the suffix '-ness', which converts adjectives into nouns describing a quality or state. This is a standard English word-building pattern.
English loves adding '-ness' to describe qualities—it's such a productive suffix that we can understand new words instantly even if we've never heard them before!
Complete word intelligence in one call. Free tier — 50 lookups/day.