My thesis describes how methods from Formal Concept Analysis can be used for constructing and extending description logic ontologies. In particular, it is shown how concept inclusions can be axiomatized from data in the description logics 𝓔𝓛, 𝓜, Horn-𝓜, and Prob-𝓔𝓛. All proposed methods are not only sound but also complete, i.e., the result not only consists of valid concept inclusions but also entails each valid concept inclusion. Moreover, a lattice-theoretic view on the description logic 𝓔𝓛 is provided. For instance, it is shown how upper and lower neighbors of 𝓔𝓛 concept descriptions can be computed and further it is proven that the set of 𝓔𝓛 concept descriptions forms a graded lattice with a non-elementary rank function.