Eros
Etymology
Greek "eros" named desiring love, personified as the god Eros (the Roman Cupid). Plato’s Symposium turned it into a ladder climbing from bodily attraction to love of beauty itself; Freud later took it as the life-drive. It gives us "erotic."
noun · /AIR-oss/
Passionate desire and romantic or sexual love.
What it names
It isolates the appetitive, longing kind of love from the many other bonds English lumps under one word.
Example
The marriage counselor distinguished eros from the deeper companionship beneath it, so the couple would not mistake one cooling for the other.
Related idea
The appetitive one among the Greek loves; compare the fixated longing of limerence, and its selfless opposite agape.