Abstract
In many languages, some words can be written in several ways. We call them variants.
Values of all their morphological categories are identical, which leads to an identical morphological tag. Together with the identical lemma, we have two or more wordforms with the same morphological description.
This ambiguity may cause problems in various NLP applications. There are two types of variants - those affecting the whole paradigm (global variants) and those affecting only wordforms sharing some combinations of morphological values (inflectional variants).
In the paper, we propose means how to tag all wordforms, including their variants, unambiguously. We call this requirement "Golden rule of morphology".
The paper deals mainly with Czech, but the ideas can be applied to other languages as well.