Optical resolution, 
σ_{Patt} and σ_{sph} are the standard uncertainties of Gaussians fitted to the origin peak of the Patterson function of the diffraction data set and the origin peak of the spherical interference function, respectively 


R_{merge} (merging R factor), 
<I(hkl)> is the mean of the several individual measurements I_{i}(hkl) of the intensity of reflection hkl 


R_{meas} or R_{r.i.m} (redundancyindependent merging R factor), 
<I(hkl)> is the mean of the N(hkl) individual measurements I_{i}(hkl) of the intensity of reflection hkl 


R_{p.i.m.} (precisionindicating merging R factor), 
<I(hkl)> is the mean of the N(hkl) individual measurements I_{i}(hkl) of the intensity of reflection hkl 


R_{anom} (anomalous R factor), 
<I(hkl)> is the mean intensity of the Friedel mates of the reflection hkl, or 


R_{Cullis} (Cullis R factor for isomorphousreplacement applications), 
F_{P}, F_{PH} and F_{H} are the structure factors for the protein, the heavyatom derivative and the heavy atoms alone, respectively 


PP_{iso} (phasing power for isomorphousreplacement applications), or, as in the program SOLVE, 
F_{P}, F_{PH} and F_{H} are the structure factors for the protein, the heavyatom derivative and the heavy atoms alone, respectively 


R (crystallographic R factor) and R_{free} (free R factor), 
R_{free} is defined as the crystallographic R factor but for a subset of reflections that have been excluded from refinement 


RSRF (realspace R factor), 
ρ_{1} and ρ_{2} are the electrondensity maps calculated from the structural model and from the experimental data, respectively 


R.m.s.d.'s of geometric parameters x, 
x_{i} are the individual values, ideal or observed, of the geometric parameter x and the sum is over all N x_{i} observed. The geometric parameters x may be bond lengths, bond angles, dihedral angles, chiral volumes, deviations from planarity etc. 


DPI (diffractioncomponent precision index), 
N_{atom} is the number of atoms in the structure, N_{hkl} is the number of reflections, N_{para} is the number of refined parameters, R is the crystallographic R factor, d_{min} is the nominal resolution and C is the fractional completeness of the data set 