passing of years; aging over time
Refers to the effect of time on objects, materials, or conditions; often used in technical or formal contexts such as 経年変化 (secular change) or 経年劣化 (aging deterioration).
This building is deteriorating due to aging.
It is necessary to design taking secular change into account.
Compound of 経 (passage of time) and 年 (year). The exact historical derivation is uncertain, but the meaning is transparent from the kanji.