heaviness

(n) the property of being comparatively great in weight
- the heaviness of lead
weightiness,
(n) persisting sadness
- nothing lifted the heaviness of her heart after her loss
(n) 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
ponderousness,
(n) used of a line or mark thickness,
(n) unwelcome burdensome difficulty burdensomeness, onerousness, oppressiveness,

weightiness ponderousness thickness burdensomeness onerousness oppressiveness

weightlessness lightness