Well, this is an interesting kanji, as it has a lot of meanings.
こころ (kokoro) as it is read, means “heart”. But now I ask you: what is a heart?
If you answered “an organ without which humans or living beings cannot live”, I cannot say it is wrong. But in Japanese that’s called 心臓 (しんぞう, shinzou), which specifically points to the organ itself.
こころ has a more abstract and vast meaning, that changes depending on the context it is in.
It is associated with human mind, feelings, emotions, will, knowledge, compassion, love, spirit, intention, and so on.
Here are some examples of words that use this kanji!
関心 (かんしん, kanshin) – interest, concern
中心 (ちゅうしん, chuushin) – center
心臓 (しんぞう, shinzou) – heart (organ)
心地 (ここち, kokochi) – feeling, sensation, mood
心配 (しんぱい, shinpai) – worry, concern, anxiety
心理 (しんり, shinri) – state of mind, mentality
安心 (あんしん, anshin) – relief, peace of mind
心強い (こころづよい, kokorozuyoi) – heartening, reassuring
心細い (こころぼそい, kokorobosoi) – helpless, hopeless
一心に (いっしんに, isshinni) – wholeheartedly
初心 (しょしん, shoshin) – original intention, initial resolution
熱心 (ねっしん, nesshin) – zeal, enthusiasm
本心 (ほんしん, honshin) – true feelings
下心 (したごころ, shitagokoro) – secret intention, ulterior motive
So if you visit a doctor, don’t say that your “kokoro” hurts! He will answer “have you been dumped?”, or something similar!
And if you confess to someone don’t give your “shinzou”! Otherwise you won’t be able to live anymore! 😀