Sweetness-light is an unusual and poetic term that is difficult to find synonyms for. However, some words that may come close in meaning could include: radiance, luminescence, warmth, tenderness, kindness, gentleness, care, love, affection, compassion, grace, beauty, charm, and good-naturedness. Each of these words hints at a sense of goodness, purity and lightness that can be associated with sweetness. Used together, words like "radiant sweetness" or "warm tenderness" can conjure the same feeling of light-heartedness that sweetness-light can. Ultimately, the perfect synonym for sweetness-light may simply be found in the words of a beautiful poem or piece of literature.