This part of the UNE 18-076 standard, Generalities, contains a series of data and specifications: Terminology, definitions, symbols and indications in order to facilitate the use of the other parts of the Standard that refer to measurements and their verification for cylindrical grooves with involute profile, metric module, centered on flanks. The range of moduli to which it applies is 0.25 to 10 inclusive, related to nominal pressure angles of 30°, 37.5°Dy450. Linear measurements are expressed in millimeters and angular measurements are expressed in sexagesimal degrees.