Nutrient
Etymology
From Latin "nutrient-," the stem of "nutriens," present participle of "nutrire" (to nourish, feed, suckle). The same root gives us "nurse," "nurture," and "nutrition" — all circling the idea of feeding something into growth.
noun · /NOO-tree-uhnt/
A substance in food the body needs to grow, repair itself, and function.
What it names
A handle for what food is made of that actually keeps you alive — the material, not the energy.
Example
Leafy greens are low in calories but dense in nutrients like iron and folate.
Related idea
Nutrients split into macronutrients — carbohydrate, protein, fat, needed in bulk and carrying calories — and micronutrients, the vitamins and minerals needed in trace amounts. A food can be calorie-rich yet micronutrient-poor, or the reverse.