letzterem

Letzterem is not a standalone entry in standard German dictionaries. It is not a common or accepted lexical item in mainstream usage. In many cases, it may appear as a misspelling or misdeclension of other forms derived from the word let zter, or it may reflect a confusion with the pronoun forms der Letztere/die Letztere/das Letztere that mean “the latter.” The correct, conventional forms depend on gender, number, and case.

In practice, the intended meaning is usually expressed with one of the standard forms for the last one or the latter. For indicating “the last one” as a noun, German uses der Letzte (masculine), die Letzte (feminine), das Letzte (neuter), and the plural die Letzten. Cases alter these forms: dem Letzten (dative), des Letzten (genitive), den Letzten (accusative) and so on, with corresponding feminine and neuter variants.

To refer to the second of two items, the pronoun forms der Letztere/ die Letztere/ das Letztere are used, as well as their plural die Letzteren. Dative examples include dem Letzteren for masculine or neuter, der Letzteren for feminine or plural, depending on the exact reference.

Usage notes: Letzterem is generally avoided in standard writing. When you mean “the last one,” use der Letzte/ die Letzte/ das Letzte or the plural Letzten; when you mean “the latter,” use Letzterer/ Letztere/ Letzteres (singular) or Letzteren/ Letzteren (plural) as appropriate.

See also: Letzte, Letzterer, Letzteren, Letzteres, German grammar on adjective declension and pronoun usage.