This is a sort I use to help students identify the vocabulary in addition and subtraction word problems that indicate which operation is needed. The sort can be used both as a math center and for individual practice. Each of my students had his/her own sort which was pasted in their math journal at the end of the unit. I used it as a warm up while we were covering addition and subtraction. The day it was introduced it was a 30- 40 minute lesson including discussing vocabulary, addition, and subtraction.The sort also includes an answer key, as well as a short set of practice word problems with an answer key.