This is the 8913th most frequent Japanese word.
残ら
"残ら" is the stem form of the verb "残る," meaning "to remain" or "to be left."
In this sentence, '残る' is used to describe the state of something that remains or is left over after others are gone.
写真が一枚だけ残りました。
Only one photo remained.
Here, '残る' is used metaphorically to describe something persisting or staying present mentally.
試験が終わった後に、覚えた内容が頭に残った。
After the exam ended, the learned content remained in my mind.
In this context, '残る' refers to an excess amount of something remaining after completion of an activity.