A patient's mandibular first molar is positioned one full premolar width distal to its normal Class I relationship with the maxillary first molar. How is this molar relationship classified?

Angle's classification of occlusion is based on the mesiobuccal cusp of the maxillary first molar and its relationship to the buccal groove of the mandibular first molar. Class I: the mesiobuccal cusp of the upper first molar occludes in the buccal groove of the lower first molar (normal). Class II: the mandibular arch is positioned distally — the mesiobuccal cusp of the upper first molar occludes anterior to the buccal groove of the lower first molar. Class II Division 1 has proclined upper incisors; Class II Division 2 has retroclined upper central incisors. Class III: the mandibular arch is positioned mesially — the mesiobuccal cusp of the upper molar occludes posterior to the buccal groove of the lower first molar.