Sigma notation looks intimidating until you read it as a story: “Add these, from here to there.” The index is the who. The bounds are the when. The expression is the what. Change any one and you change the story. Summation isn’t “add everything”… it’s “add exactly what matters.” That means choosing the right unit (student, class, day) and the right window (this week, this term). It also means deciding what not to include on purpose, not by accident. Σ is permission to zoom out without losing track of the pieces. Use it to collect small truths into a useful whole. Highlight what counts; leave the rest unbolded.
