Noun
すうねん
数年がすぎさった。
Several years passed.
数年前まで、日本に住んでいました。
I lived in Japan until a few years ago.
この絵が完成するには、あと数年かかります。
It will take several years for that painting to be complete.
When a number of years have passed you say that several years have passed! You don't want to say how many years, so just say several years.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.