This part of ISO 25239 defines friction stir welding terms. In this part of ISO 25239, the term “aluminium” refers to aluminium and its alloys. NOTE In addition to terms in English and French (two of the three official ISO languages), this part of ISO 25239 gives the equivalent terms in German; these are published under the responsibility of the member body for Germany (DIN). However, only the terms and definitions given in the official languages can be considered as ISO terms and definitions.