The concept of correlations as an indicator of cross-compliance and relations has been widely used not only in natural sciences and in engineering. It is also increasingly viewed in the sub-sectors of social sciences and the humanities, to describe the interrelation between phenomena, concepts, events, etc. In this study, correlation is used as a measure of relation to determine how strong and interacting the relationship between two different systems is – the principles of modern didactics and the functions of a learning tool, respectively, application capabilities. The handbook essentially is a compilation of the main information for practical purposes. It is a type of teaching aids in which development and preparation of certain didactic principles, such as scientific and visualization, systematic and sequence, readability, accessibility, are respected. However, a modern learning process is inconceivable without several other didactic principles as well (e.g., free creative activities, positive emotional background of learning, linking learning experience to real life, intellectual activities and self-expression options of pupils, etc.). When designing a handbook for use in the electronic environment, a balance between the conditions of good practice in the didactics and opportunities and limitations of technologies must be found. The handbook uses various technological solutions: (1) Multimedia allows using text, pictures, audio, and video in the explanation of study content. (2) Hyperlinks allow providing quick access to appropriate information both in different sections of the handbook and on the Internet. (3) Interactivity, which ensures the involvement of the learner in the learning process, the choice of topics and the order in which they are acquired, and to perform self-testing tasks, etc. The handbook is developed by implementing best practices in responsive design, i.e., the content of the material is equally well-comprehensible on different screens (computer screen, tablet, smartphone). The object of the research is the “Latvian Language Handbook” („Latviešu valodas rokasgrāmata”; valodasrokasgramata.lv), which has been developed as a multifunctional informative practical electronic tool for any Latvian language learner. The study aims to characterize a tripartite correlation between 1) adherence to didactic principles in the development of electronic teaching aid, 2) human learning habits, and 3) the opportunities and limitations of modern technology. To achieve the aim of the study, it is important to clarify several issues: - Whether technology is a sufficiently motivating language learning tool that could lead to a waiver of one or another of the didactic principles; whether the correlation can be characterized as a mutually positive factor, i.e., the more limited the potential of the electronic learning tool, the more effective the respect of didactic principles should be, and vice versa. - How current capabilities (text, audio, images, and interactivity) offered by an electronic learning tool correlate with the learner’s creativity, and self-expression; tests and self-tests do not allow for several correct solutions, they must be “unambiguous”, verifiable with computer tools.