onerous
UK: ˈəʊ.nər.əs | US: ˈoʊ.nɚ.əs
adj. involving great effort or difficulty; burdensome
adj. (law) imposing legal obligations that are difficult to fulfill
Derived from Latin onerosus ("burdensome"), which stems from onus ("load, burden"). The root oner- preserves the core meaning of weight or obligation, while the suffix -ous (from Latin -osus) denotes possessing a quality. The word evolved through Old French onereus before entering Middle English, retaining its original sense of heaviness—both literal (physical weight) and figurative (legal/emotional burden).
The contract imposed onerous financial penalties for late delivery.
Climbing the mountain with full gear proved to be an onerous task.
Small businesses often struggle with onerous regulatory requirements.
She found the responsibility of caring for three siblings emotionally onerous.
The treaty placed onerous restrictions on the defeated nation.