The object of this study are love-words in the earliest mainstream Christian literature. In the first chapter, we define what a love-word is and how our systematic analysis of love-words contributes to the debate on alternative Christianities first proposed by Walter Bauer. In the second chapter, we discuss our methods and their limitations. We focus on indentifying with as much accuracy as possible how each love-word relates to significant themes in the context. For instance, a love-word can be connected to an anthropological theme, to a soteriological theme, to a christological theme, to an ecclesiological theme, to an eschatological theme or to all these themes at once. In particular, we discuss in detail how the author lets a love-word interplay with other important ideas in the context of a book and vice versa. This analysis shows that love-words can be categorized on the basis of the ideas connected to them. Our work identifies the co-text of love-words, that is, the words and ideas that typically co-appear with love-words. One important factor in our study is the relationship between love-words in the Hebrew Scriptures, and their Greek counterpart in the Septuagint, and those in the New Testament. This divides our study naturally in two parts. In chapter three, we have analysed love-words in the writings that most likely may have influenced the earliest mainstream Christian authors and were written before the Christian tradition arose. In chapters four through seven we discuss the New Testament literature: the Synoptic Gospels (chapter four), the Johannine literature (chapter five), the Pauline literature (chapter six), and the remaining New Testament books in chapter seven. In chapter three, we have included next to the Hebrew Scritpures and their Greek translation known as the LXX also the biblical and the non-biblical Dead Sea Scrolls, some Apocrypha, and some pseudepigraphical books of interest. Finally, this extensive study of love-words identifies common patterns in the usage of love-words shared by different authors of the New Testament. Using the ideas that connect to a love-word we are able to define meaningful love-categories. It turns out that some of these categories are considered by the authors of the early mainstream Christian books themselves as signposts, as distinguishing marks of mainstream Christianity. They are, on the one hand, a significant part of what distinguishes Christianity from other teachings. On the other hand, some of these love-categories are a condition sine qua non, i.e., without them there would be no Christianity at all. In the concluding chapter, we list the most important and surprising features and categories which set apart the early mainstream Christian understanding of and teaching on love.