Czech inflection system shows a great variation of forms, both standard and non-standard. This variation supports functional differences in the Czech national language, however it also makes the language learning process more difficult for foreign language speakers. The variation is caused by the asymmetric dualism of a language sign; the signifier and the signified are not in a perfect correlation. Czech formal morphology is being formed by both unifying and differentiating tendencies. The role of usage in Czech language codification also remains unresolved. These and other factors cause a rather confusing situation. Means of variation can be classified into two groups: equivalent (both the function and style enable free interchangeability; e.g. po otcově / otcovu odjezdu = after father`s departure) and synonymous variants which are used for differentiation either in style (e.g. Američané x Američani) or in semantics (e.g. ve výkladu x při výkladu). From a point of view of language teaching we recommend the standard neutral and colloquial forms to be presented for active acquisition; presentation of exceptions is only useful for the highly frequent ones.