This is the 5079th most frequent Japanese word.
親切
Kindness; helpfulness.
In this sentence, '親切' is an adjective that describes someone's kind and caring personality.
彼女はとても親切ですから、皆に好かれています。
Since she is very kind, everyone likes her.
Here, '親切' refers to an act of kindness or thoughtfulness extended to the speaker.
親切にしていただいてありがとうございます。
Thank you for being kind to me.
The word '親切' is used as an adjective to characterize individuals who show kindness.