(JeffK) I think, that a tankette didnt have a turret, therefore a German Pzkw I is a light tank and an Italian CV-33 is a tankette.
No, tankettes could have turrets - examples of tankettes include:
French: AMR 33 (with rotating turret)
Japanese: Type 94 Te Ke (with rotating turret)
The problem is (i think): there isn't a great definition for tankettes. One defintion is: "A tankette is a type of lightly armed and armored tracked combat vehicle resembling a small tank roughly the size of a car, mainly intended for light infantry support or reconnaissance. Colloquially it may also simply mean a "small tank"."