(chemistry) The uncharged radical H₂N^. formally derived from ammonia by removing a hydrogen atom; and any of its derivatives R₂N^.

(chemistry) The uncharged form of an aminoxide derived from hydroxylamines by removal of a proton; their structure is best represented as R₂NO^. <=> R₂N^(.+)-O⁻.

(chemistry) A positively charged radical ion.

(geometry) A point at which the radical lines of three circles meet. / Pertaining to radical centrism.

(mathematics) The line containing the locus of points from which the segments respectively tangent to two given circles have equal length.

(chemistry) A negatively charged radical ion.

(chemistry) Any radical that also carries an electric charge; typically, the charge and unpaired electron are associated with the same atom.