means A substance—like a protein, vitamin, or mineral—that a living thing needs to take in for energy, growth, and staying alive.

from From the Latin verb 'nutrire,' meaning to nourish or suckle—the same root that feeds 'nourish,' 'nurse,' and 'nurture.' 'Nutrient' is the present-participle form, 'nutriens,' literally 'nourishing,' and entered English as a scientific term for the things that do the nourishing. The original image is maternal: feeding a child at the breast.