Card is the function on theclassofall ordertypes definedby Card(σ)=|a|; where〈a,r〉 If 〈a,r〉,〈b,s〉 are structuressuch that〈a,r〉≅〈b, s〉thenalso 〈a,r–1〉≅〈b, s –1 〉..