This is the 3275th most frequent Japanese word.
年長
"Older" or "eldest" (often referring to age or seniority).
The term '年長' is used to denote that he is of more age than the speaker.
彼は私より三歳年長です。
He is three years older than me.
Here, '年長' refers to being part of an older age group or grade.
年長のクラスではリーダーになるチャンスがあります。
In the senior class, there is an opportunity to become a leader.
In this context, '年長者' refers to people who are older in age, highlighting respect for seniority.