This standard specifies fundamentals of maintenance. It completely structures the maintenance in basic measures and defines terms that are necessary in conjunction with terms according to DIN EN 13306 for understanding the relationships. The revision of the standard DIN 31051:2003 became necessary after CEN/TC 319 "Maintenance" had revised the European Standard EN 13306 "Maintenance terminology", which has been published as DIN EN 13306. The terms specified in DIN EN 13306 only cover a portion of the terms from DIN 31051. Moreover, a structuring of maintenance is absent in DIN EN 13306. These gaps are intended to be closed with this standard, which uses the terms defined in DIN EN 13306 as a basis. Furthermore, terms closely related to maintenance are listed for purposes of differentiation and explanation. The following modifications have been made with respect to DIN 31051:2003-06: a) the definitions of the following terms have been modified in accordance with DIN EN 13306:2010: failure, modification, item, spare part, fault, fault diagnosis, fault localisation, maintenance, repair, shutdown, improvement, availability; b) the term "Lebenszyklus" ("life cycle") has been included; c) in clause 4 "Terms and definitions" the fourth position of the decimal classification has been deleted and the terms are now listed with a three-digit numeration in alphabetical order; d) Annex B has been omitted. The standard has been prepared by Working Committee NA 152-06-07 AA "Instandhaltung" ("Maintenance") of the Fundamental Technical Standards Committee (NATG) - Technical Section "Technical production documentation" - at DIN.