Perceptual subitizing is the ability to recognize the quantity of a set without counting. It is the basis for counting and cardinality. For example, recognizing the pattern of five dots on a dice as "5".
Conceptual subitizing is seeing number patterns within a set (part—whole) and then determining the quantity by putting the number patterns together . For example, when shown a domino with a pattern of 8 dots/pips the observer may break the 8 dots into two groups of 4