It can be used in various contexts:
* Renai shōsetsu (恋愛小説): Romance novel
* Renai kankei (恋愛関係): Romantic relationship
* Renai jōsei (恋愛事情): Love life
* Renai suru (恋愛する): To be in love
* Renai de (恋愛で): Due to love
It is a very common word in Japanese and often used in daily conversation, especially in relation to romantic relationships.