throughout; over a period of; over a span of
Used with time or spatial expressions to indicate that something extends across a whole range or period. Often appears as にわたって or にわたり.
The meeting continued for three hours.
He has been conducting research in this field for many years.
Standard kanji spelling for this expression.
Alternate kanji spelling using 亘, which is less common but still seen.
Derived from the verb 渡る (to cross, to extend over) combined with the particle に, grammaticalized into an expression indicating a span of time or space.