index names exist in dba_indexes but not in dba_segments

dear friends,

I'm a little confused about the following behaviour because
in my case I've a schema owner with 28242 Indexes. All index names in the view dba_segments are also  in the view dba_indexes. They are exactly 4276 Indexes.
But I've got lots of indexnames in the view dba_indexes where not exist in the view dba_segments.
I have not any  virtual indexes and the hidden parameter "_use_nosegment_indexes" are not in use. Can any one tell me the reason for this behaviour?

Thank you very much for all suggestions

best regards
Stefan