I can’t count the number of times I heard my mother say, “Here, take mine,” when I was growing up.

After she said this, she’d offer me or one of my siblings something from her plate—her piece of cake, the rest of her French fries, her pancakes. It was her portion of the meal, but she willingly sacrificed and gave it to us.

My mother’s willingness to offer me something that belonged to her beautifully illustrates the meaning of the word “portion” that appears more than one hundred times in...