also: じゅうか
heavy load; heavy burden; heavy freight
Concrete use for something physically heavy that is carried, borne, or transported. The reading おもに is the ordinary one; じゅうか is much less common and sounds more technical or freight-related.
The horse went along the mountain path carrying a heavy load.
heavy responsibility; mental burden; encumbrance
Only with reading おもに
Figurative use for a responsibility, obligation, worry, or relationship that feels emotionally or practically oppressive. Common in patterns such as 重荷になる and 重荷を背負う.
The responsibility of supporting his family was a heavy burden for him.
That promise had become a burden to her.
The monthly loan payments have become a burden.
He carries the heavy burden of supporting his family.
Now that the project is over, I could finally set down the burden.
Her one remark lightened my burden.