Nestle-Aland is a common reference to a modern Greek language version of the New Testament, the Novum Testamentum Graece, named after the scholars who led the critical editing work. The text, edited by the Institut für neutestamentliche Textforschung at the University of Munster (Germany) is currently in its 27th edition, abbreviated NA27. The NA27 is used as the basis of most contemporary New Testament translations, as well as being the standard for academic work in New Testament studies. It should be noted that the Greek text of the 27th edition is virtually identical to the 4th edition of the United Bible Societies Greek New Testament (abbreviated UBS4).
The Nestle-Aland Greek text is based on what biblical textual scholars refer to as the "critical text". The critical text is an eclectic text compiled by a committee that examines existing (extant) manuscripts in order to weigh and select which reading is thought closest to the lost original autographs. A number of factors are used to help determine probable readings, such as the date of a given manuscript, the geographical distribution of a particular reading, and possibly accidental or intentional corruptions. Extensive footnotes (called the critical apparatus) identify a large number of textual variants, or differences found in specific manuscripts, to aid in study and evaluation.
A first edition published by Eberhard Nestle in 1898 combined the readings of the editions of Tischendorf, Westcott and Hort, and Weymouth. In 1901, he replaced Weymouth with Bernhard Weiss's text. In later edition, Nestle began noting the attestation of certain important manuscripts in his footnote apparatus.
Eberhard's son Erwin Nestle took over after his father's death and issued the 13th edition in 1927. This edition introduced a separate critical apparatus and began to abandon the majority reading principle.
Kurt Aland became the associate editor of the 21st edition in 1952. At Erwin Nestle's request, he reviewed and expanded the critical apparatus, adding many more manuscripts. This eventually led to the 25th edition of 1963. The great manuscript discoveries of the 20th century had also made a revision of the text necessary and, with Nestle's permission, Aland set out to revise the text of Novum Testamentum Graece. Aland submitted his work on NA to the editorial committee of the United Bible Societies Greek New Testament (of which he was also a member) and it became the basic text of their third edition (UBS3) in 1975, four years before it was published as the 26th edition of Nestle-Aland.
The current edition of Nestle-Aland reproduces the text of NA26 (the same text used in UBS3 and UBS4). The 27th edition presents a heavily revised critical apparatus and a rewritten introduction.