## 5 Summary and Conclusions  
The qualitative evaluation of truss structures featured in this paper was used for tensegrity form finding. New, precise definition was proposed. Characteristic features of tensegrity structures were used to classify the structures described in the literature as \"pure tensegrities\" or \"structures with tensegrity features\". Only in the case of pure tensegrities (structures with all six characteristic features) is it possible to control truss properties, such as stiffness and natural frequency, by changing the level of self-stress. The existing form-finding methods determine the self-equilibrated configuration in the absence of externally applied loads, but they are not always define other characteristic features of tensegrity structures. The identification of the self-stress state in a truss is not sufficient to call it a tensegrity structure. From the point of view of structural mechanics, one of the most important tensegrity features is the mechanism--the uniqueness of tensegrity structures is based on the fact that self-stress states stabilize existing infinitesimal mechanisms. The absence of the mechanism brings the trusses into the group of structures with tensegrity features. In this paper, singular value decomposition of the compatibility matrix was used to determine the states of self-stress and mechanisms. The nonlinear analysis with the use of geometric stiffness matrix, which takes into account the impact of the self-stress state was used to establish whether  
Figure 12: Truss with no tensegrity features: (**a**) values of self-stress state, (**c**) mechanism for truss shown in (**b**). the mechanism was infinitesimal or finite. The other characteristic features of tensegrity structures, that satisfy the condition of discontinuous compression members and the inclusion of compression components inside the set of tension components (cables) were determined indirectly by the identified self-stress state. The compatibility matrix and the stiffness matrix with the effect of self-equilibrated forces were determined using the finite element method. The geometrical and material characteristics were not taken into account because the characteristic features of tensegrity structures do not depend on them. The proposed method of evaluation allowed a precise understanding of this unusual structure and a way to specify the correct use of this term in these applications. The results are summarized in Table 1. Some 2D pure tensegrity structures (according to the proposed definition) exist, but most of the trusses are incorrectly named in the literature. The term \"tensegrity\" is misused and overused in the literature. Three pure tensegrities can be distinguished, with one infinitesimal mechanism stabilized by one self-stress. Three other more complex structures are pure tensegrities with two infinitesimal mechanisms stabilized by one self-stress. In conclusion, tensegrity is overused in the literature on the subject, in particular, in the field of 2D models, where intuitive understanding of the specific features should be the easiest. Examples of pure tensegrities shown in Figures 5a and 6, and their extensions, can be recommended as 2D computational models for use in the coverings for stadiums and halls. The schemes from Figure 8 can be the basis for the construction of 2D metamaterials with specific mechanical features. The unit cells presented in Figures 5a and 8 are recommended as metamaterial unit cells. It should be noted that tensegrity trusses with computational schemes presented in Figures 5a, 6 and 8 can be successfully applied as deployable or smart engineering structures with monitoring, self-control, self-repair, and active control. **Author Contributions:** Introduction was prepared by [PERSON] and [PERSON]. Definition of tensegrity and mathematical description were written by [PERSON], [PERSON] and [PERSON]. Results were obtained by [PERSON] and [PERSON]. The analysis of the results and conclusions were written by [PERSON] and [PERSON].