Previous effort on ontology learning has focused on discovering generic relatedness or associations rather than specific types of relations. Among different types of specific relations, the taxonomic relation has been discussed most frequently. Other types of relations, although much less studied, are also important to some domains. For example, part-whole relation is critical to Sequence Ontology for genomic annotation and related-synonym is part of Gene Ontology. Some efforts have been taken to discover part-whole relationship from the text and in learning instances of relations from the Web. Additional research work is needed in discovering specific relations by ontology learning.