Glossary:Ordinal number
ordinal number - number assigned to each element indicating the importance of the element. The lower the ordinal number, the greater the importance. By default, ordinal number is set to the number of elements in the current collection. This way, the first element you add will have the ordinal two (the root of the knowledge tree gets the ordinal one), second element will get three, etc. Ordinal numbers are useful in sorting the collection or its subsets