Gary Chapman opens The 5 Love Languages with his foundational, highly influential framework: individuals characteristically experience and express love through one or more of five distinct "love languages" — words of affirmation, quality time, receiving gifts, acts of service, and physical touch — with most people having a clear primary preference among these five.

Chapman's foundational argument:

• He draws on his extensive marriage counseling experience to argue that much relationship conflict and dissatisfaction stems not from genuine lack of love between partners, but from partners expressing love through their own preferred language while their partner's actual primary love language differs, meaning the love expressed doesn't register as clearly to the receiving partner as intended
• Chapman argues that identifying both one's own and one's partner's specific primary love language provides considerably more effective, targeted guidance for expressing love in a way that genuinely registers, compared to expressing love in whatever manner feels natural to the giving partner without this specific awareness
• This foundational framework, while originally developed within Chapman's specifically Christian marriage counseling practice, has achieved considerably broader secular popularity and application across dating, marriage, family, and even workplace relationship contexts

This foundational framework sets up the book's overall structure: detailed examination of each of the five specific love languages, along with practical guidance for identifying one's own and one's partner's primary language and adjusting expression accordingly.