Severalquadrilateralshaperegularmeshconditionscommonlyusedinthefiniteelementmethodareproventobeequivalent.Theirinfluenceonthefiniteelementinterpolationerrorandtheconsistencyerrorcommittedbynonconformingfiniteelementsareinvestigated.TheeffectoftheBi-SectionConditionanditsextendedversion(1+α)-SectionConditiononthedegeneratemeshconditionsisalsochecked.ThenecessityoftheBi-SectionConditioninfiniteelementsisunderpinnedbymeansofcounterexamples.
