Günaydın! They are different. 1. If you talk about your biological heart, you should use "kalp". 2. If you talk about emotinal situations(for example love) you should use "gönül". 3. If you talk about courge you should use "yürek". However, sometimes we might use some of them interchangeably(not very often). But, I suggest you to use those words in the order above. Some examples: Kalp sağlığını korumalısın. You should protect your heart health. Gönül işlerinde çok şanslıyımdır. I am very lucky at romantic relationships. (this is not a direct translation) Yüreği yetiyorsa gelecektir. If he has enough courge, he will be here. (this is not a direct translation)

Yürek and Kalp are literally ( فِ عِلمِ لُقَتِ) the same. Kalp is an Arabic loanword (قلب), yürek is turkish. But we dont use them interchangebly. And interestingly we use kalp more. Gönül is different. What Furkan said is true but i will make an addition. For the hearts of animals we may use yürek. Especially in Eid al Adha

Çok teşekkür ederim Emre :)

Yürek ve kalp aynı anlamda kullanılır.(bir organ ismi) Gönül ise sevgi , aşk anlamında kullanılır.