Which four Greek terms for kinds of love does C.S. Lewis discuss in The Four Loves?

In The Four Loves, C.S. Lewis discusses storge, philia, eros, and agape.

The 1960 book develops ideas first presented in a series of BBC radio talks. Lewis uses Greek vocabulary to distinguish affection, friendship, romantic love, and charitable or self-giving love. His categories are explanatory rather than a complete scientific classification of every human relationship.

Storge refers to natural affection, especially within families. Philia concerns friendship, eros describes romantic or sexual love, and agape names a selfless form of love associated with Christian charity.

Readers sometimes substitute related Greek words such as philia and philos or translate agape simply as “love.” Lewis’s purpose was to show how different kinds of love can overlap and how each can become distorted when treated as an absolute.