This is the 7316th most frequent Japanese word.
了
"Finished" or "complete."
The character '了' is used in '終わりました', which means 'finished'. Here, '了' indicates the completion of the action.
試験が終わりました。
The exam has finished.
The character '了' appears in '上映されました', suggesting completion of the movie's showing.
映画が上映されました。
The movie has been shown.
'了' in '完了しました' emphasizes the reaching of the end or completion of the plan.