Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
pleasantness is a noun meaning "the feeling caused by agreeable stimuli; one pole of a continuum of states of feeling". It carries 2 recorded senses.
the feeling caused by agreeable stimuli; one pole of a continuum of states of feeling
the quality of giving pleasure
“he was charmed by the sweetness of her manner”
“the pleasantness of a cool breeze on a hot summer day”
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 pleasantness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.