Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
heaviness is a noun meaning "the property of being comparatively great in weight". It carries 5 recorded senses.
the property of being comparatively great in weight
“the heaviness of lead”
persisting sadness
“nothing lifted the heaviness of her heart after her loss”
an oppressive quality that is laborious and solemn and lacks grace or fluency
“a book so serious that it sometimes subsided into ponderousness”
“his lectures tend to heaviness and repetition”
unwelcome burdensome difficulty
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 heaviness come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.