Some additional information!
Rei-shiki Kanjo Sentoki (Formal Japanese Name)
Abbreviated as.....
'Kansen' (Kanjo Sentoki) Carrier Fighter
'Reisen' (Rei Sentoki) Zero fighter Aircraft
'Zero sen' (Zero Sentoki)
Allied Code name : "Zeke" or more commonly referred as 'Zero'
A6M2 Designation
A = Carrier Fighter
6 = Sixth Type or Version
M = Mitsubishi (Manufacturer)
2 = Second Version of Design
Model 21 Description (correct description is Model Two-One rather than twenty one.)
2 = Second Airframe Modification
1 = First Engine Configuration
A6M5 Designation
A = Carrier Fighter
6 = Sixth Type or Version
M = Mitsubishi (Manufacturer)
5 = Fifth Version of Design
Model 52 Description
5 = Fifth Airframe Modification
2 = Second Engine Configuration