Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
plainness is a noun meaning "the state of being unmixed with other material". It carries 4 recorded senses.
clarity as a consequence of being perspicuous
the appearance of being plain and unpretentious
an appearance that is not attractive or beautiful
“fine clothes could not conceal the girl's homeliness”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for plainness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.