This is the 2268th most frequent Japanese word.
退職
"Retirement" or "resignation" from a job.
In this sentence, '退職しました' is used in the past tense to indicate the act of retiring from a job.
私は昨年、退職しました。
I retired last year.
Here, '退職すること' is a noun phrase formed with the verb '退職する', suggesting the potential plan to retire.
父は会社を退職することを考えています。
My father is considering retiring from his company.
In this example, '退職後' is a noun indicating the time after the act of retiring.