Years is a plural noun for a word "Year."
Year- 1. The time taken by the earth to make one revolution around the sun.
2. The period of 365 days (or 366 days in leap years) starting from the first of January, used for reckoning time in ordinary circumstances.
3. One's age or time of life.
4. A very long time; ages.
5. A set of students grouped together as being of roughly similar ages, mostly entering a school or college in the same academic year.
Krushna is seven years old.