Connection system for components through which fluid flows, comprising at least one connection component and a union nut, wherein the connection component has at least • a first cover which forms an internal tubular passage having a predetermined longitudinal extent which extends at least partially along a first central axis, and • a groove which is arranged in the first cover outwardly with respect to the passage and which extends at least partially around the first cover in an axial portion of the first cover, wherein the union nut has at least • a second cover which forms an internal receiving region having a predetermined longitudinal extent which extends at least partially along a second central axis, and • an engagement element which is arranged on the second cover inwardly with respect to the receiving region and which extends at least partially along an axial portion of the second cover, wherein • the first axis and the second axis are arranged substantially one on the other and form a common axis (A1, A2), • the passage is received at least partially in the receiving region of the union nut, and • the engagement element is at least partially received in the groove, wherein the engagement element and the groove form a positive-locking connection which is azimuthal with respect to the common axis (A1, A2) between the connection component and the union nut in order to prevent a rotation movement of the connection component with respect to the union nut about the common axis (A1, A2), wherein the connection system has a connection pair or a large number of connection pairs of joining elements, and the connection pairs have at least one joining element which is arranged on the groove and a second joining element which is arranged on the engagement element, wherein the first joining element is a projection or a receiving element and the second joining element is a corresponding receiving element or a corresponding projection, and wherein the projection and the receiving element of the connection pairs are arranged in such a manner that the surface shape of the projection at least partially corresponds to the surface shape of the receiving element, the projection engages at least partially in the receiving element and thereby forms the positive-locking connection which is azimuthal with respect to the common axis (A1, A2) between the connection component and the union nut, and form a positive-locking connection which is axial with respect to the common axis (A1, A2) between the connection component and the union nut in order to prevent a linear displaceability of the connection component with respect to the union nut, the union nut has a thread which is arranged on the second cover inwardly with respect to the receiving region and which extends at least partially along the axial portion of the second cover, characterised in that the union nut has on the second cover apertures which extend at least partially along an axial portion of the second cover and adjacent thereto there are formed in the second cover webs on which the portions of the thread are arranged. • a first cover which forms an internal tubular passage having a predetermined longitudinal extent which extends at least partially along a first central axis, and • a groove which is arranged in the first cover outwardly with respect to the passage and which extends at least partially around the first cover in an axial portion of the first cover, • a second cover which forms an internal receiving region having a predetermined longitudinal extent which extends at least partially along a second central axis, and • an engagement element which is arranged on the second cover inwardly with respect to the receiving region and which extends at least partially along an axial portion of the second cover, • the first axis and the second axis are arranged substantially one on the other and form a common axis (A1, A2), • the passage is received at least partially in the receiving region of the union nut, and • the engagement element is at least partially received in the groove,