Reflexivity is also known as generalized identity matching. In the example below if you select a picture of a bike as the missing picture you would be demonstrating reflexivity if you had no prior matching training or reinforcement for doing so.
Symmetry if A = B then B = A. The learner is taught when presented with the picture grapes (sample stimulus A) to select the written word grapes (sample stimulus B). When presented with the written word grapes (sample stimulus B), without additional training or reinforcement, the learner selects the picture of grapes (sample stimulus A). Applied Behavior Analysis (2nd Edition)
Transitivity is when an untrained stimulus-stimulus relation emerges as a product of training two other stimulus-stimulus relations