1) Lens 2) Lens system 3) Lense 
An anastigmat or anastigmatic lens is a photographic lens completely corrected for spherical aberration, coma, and astigmatism. Early lenses often included the word Anastigmat in their name to advertise this new feature (Doppel-Anastigmat, Voigtländer Anastigmat Skopar, etc.). All modern photographic lenses are close to being anastigmatic. The fi...
Is a compound lens which has been corrected for the lens aberration ' astigmatism '. 
[n] - compound lens or lens system designed to be free of astigmatism and able to form approximately point images
noun compound lens or lens system designed to be free of astigmatism and able to form approximately point images
a compound lens corrected for the aberrations of astigmatism and curvature of field.