Ontology evaluation is one of the most important phases of Ontology Engineering. Researchers have identified different types of errors that should be catered in ontology evaluation process for fulfillment of the Semantic Web vision and classified them in error's taxonomy. We have found that some important errors are missing in the error's taxonomy. We have identified and defined two new incompleteness errors i.e. Functional Property Omission (FPO) for single valued property and Inverse-Functional Property Omission (IFPO) for a unique valued property. We have demonstrated the importance of such errors by giving different scenarios where appropriate. We have evaluated different ontologies and presented empirical results.