am­s­tex – Amer­i­can Math­e­mat­i­cal So­ci­ety plain TeX macros

AMSTeX is a TeX macro pack­age, orig­i­nally writ­ten by Michael Spi­vak for the Amer­i­can Math­e­mat­i­cal So­ci­ety (AMS) dur­ing 1983–1985 and is de­scribed in the book ‘The Joy of TeX’. It is based on Plain TeX, and pro­vides many fea­tures for pro­duc­ing more pro­fes­sional-look­ing maths for­mu­las with less bur­den on au­thors.
More re­cently, the fo­cus of at­ten­tion has switched to am­s­la­tex, but AMSTeX re­mains as a work­ing sys­tem.