This axis includes the contributions of general linguistics. Specifically, contributions that allow deepening the conceptualization of linguistic activity research from the ISD: language and society, grammar and text, relationships between languages and textual genres, linguistic diversity, text and type of discourse, structure / architecture of the text, didactics of languages as an autonomous science and their socio-political character, language and psychological development.

This axis, from the point of view of evolutionary psychology, includes the development and learning of languages in multilingual contexts (because there is no longer a totally monolingual context), among which it is worth mentioning that related to the first and second languages, minority, local, national, foreign, foreign languages, as well as ordinary and unusual development (linguistic problems, etc.).

In this axis, it is of great interest the identification of the students' learning processes with respect to the knowledge of grammar and discourse, as well as the possible transpositions to the teaching of the studies and methodologies carried out in psycholinguistics for the analysis of development and in language teaching.

This third axis focuses on the teaching of languages. We understand that much of SDI's contribution has focused on how to improve student-centred teaching practices: the elaboration of curricula and teaching materials for diverse educational levels; the development of didactic resources that foster the acquisition of the contents of learning; treatment of the contents of linguistic activity as a system of oral and written communication, as a metalinguistic reflection, as a literary culture, and as a sensitivity towards linguistic diversity and minoritised languages.

This axis also welcomes proposals that focus on various strategies and resources to foster multilingual competence: immersion in the second language, interlinguistic transfer, integrated teaching of languages, translanguaging, multimodality, computer resources, and, ultimately, a series of approaches that contribute to didactic engineering and that are useful both in multilingual teaching and in teaching the first or second language.

This axis includes studies related to teacher training, both initial and in-service. The subject can be approached from different perspectives: analysis of the teaching activity that takes place in the school context; characterization of specific professional gestures; teaching practices and tools to analyse the representations of teachers about their work; self-confrontation, questionnaires, interviews, action figures, etc.

In addition, the studies and instruments for the training of teachers working in minority languages ​​and foreign languages, language teaching to adults, literacy and literary development, in the languages ​​of the specialty, in the field of languages within higher education, bi-multilingual educational contexts, populations of immigrant origin, etc.

This axis also includes other types of work that have existed in the SDI tradition, such as the study of linguistic activity in certain professions.