Generalizations of a collection of concepts can be computed by the least common subsumer (lcs) which is a useful inference for building knowledge bases. For general FL0-TBoxes the lcs need not exist. In this thesis, we devise a condition to check whether a concept is the lcs of two concepts w.r.t. a general FL0-TBox. We also define the characterizations for the existence of the lcs. Last, we show that if the lcs exists, then we can compute the lcs and the upper bound for the role-depth of the lcs.