حُـبّ، الـحُـبّ، مَـحَـبّـة، الـمَـحَـبَّـة
You say you want to know how the word is written in Arabic, so I will not bother you with pronunciation or phonetic English spelling.
The simplest noun is حُـبّ, but as masters explained, abstract nouns in Arabic take the definite article, so, depending on context, you would in most cases say الـحُـبّ.
In Biblical contexts (as in the Gospel of John), مَـحَـبّـة is preferred. John's venerable dictum is famously sung by Umm Kulthoom as الله مَـحَـبّـة.
Since no syntax is provided, I cannot help you with case inflections, but you probably already know about these.