IPA: /ɑːrˈtɪk.jʊ.lət.nəs/
KK: /ɑrˈtɪk.jə.lɪt.nəs/
The quality of being able to express thoughts and ideas clearly and effectively.
Her articulateness during the presentation impressed everyone in the audience.
Articulateness is formed from "articulate" (from Latin "articulatus", meaning jointed or divided) and the suffix "-ness" (meaning the state or quality of). The word refers to the quality of being able to express oneself clearly and effectively, as if the thoughts are jointed together in a coherent manner.
Think of 'articulate' as expressing thoughts clearly, and '-ness' indicating a state. This helps you remember that 'articulateness' means the quality of being clear and effective in expression.