The Greek capital letter sigma, , is used as a shorthand way of indicating the sum of a set of numbers expressed with subscript notation. It sometimes appears with an index and with limits, e.g., This is read as “the sum of the i's, where i goes from 1 to 4”; thus the sum is 10. More frequently, the index appears as a subscript. Using the weights we measured for our discussion of subscript notation, When no index or limits are furnished, the summation is considered to extend over all of the scores under discussion; so X = 43 grams.