definiens: means a molecule comprising at least one polypeptide chain that is not full length, including ( i ) a Fab fragment, which is a monovalent fragment consisting of the variable light ( VL ), variableheavy ( VH ), constant light ( CL ) and constant heavy 1 ( CH1 ) domains ; ( ii ) a F(ab')2 fragment, which is abivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region ; ( iii ) aheavy chain portion of a Fab ( Fd ) fragment, which consists of the VH and CH1 domains ; ( iv ) a variablefragment ( Fv ) fragment, which consists of the VL and VH domains of a single arm of an antibody, ( v ) adomain antibody ( dAb ) fragment, which comprises a single variable domain ; ( vi ) an isolatedcomplementarity determining region ( CDR ) ; ( vii ) a Single Chain Fv Fragment ; ( viii ) a diabody, which is abivalent, bispecific antibody in which VH and VL domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with the complementarity domains of another chain and creating twoantigen binding sites ; and ( ix ) a linear antibody, which comprises a pair of tandem Fv segments ( VH - CH1 - VH - CH1 ) which, together with complementarity light chain polypeptides, form a pair of antigen bindingregions ; and ( x ) other non - full length portions of heavy and/or light chains, or mutants, variants, orderivatives thereof, alone or in any combination