10. The apparatus according to claim 6 , further comprising: an input unit configured to input image data; and a detection unit configured to detect an object based upon image data inputted by the input unit.
6. An image processing apparatus comprising: at least a processor and at least a memory coupled to the at least the processor and having stored thereon instructions which when executed by the at least the processor cooperate to act as: an extraction unit configured to extract a feature information from an object in input image data; a registration unit configured to classify a plurality of feature information into a plurality of groups based upon a similarity, and register the plurality of feature information into a dictionary, wherein the dictionary is used to determine a similarity between the feature information registered in the dictionary and the feature information extracted by the extraction unit; and a deletion unit configured to delete, among the plurality of groups, a feature information of a group, which does not reach a predetermined use level, from the dictionary, wherein a name of an identifier of the group which can be rewritten by a user is used as the use level, and wherein the deletion unit deletes, from the dictionary, a group whose name of the identifier is an initial value, as the group not reaching the predetermined use level.