I stumbled upon this phrase in a book. I then looked at Wiktionary under obrovský, and noticed that the form "obrovskýma" does not appear there. As far as I can tell it is the neuter plural declination, but in the Wiktionary table only "obrovskými" appears. Wiktionary table

My question would be: Does this declination exist for all adjectives, or is there some special condition for it? Is it related to the "dual" declination of "očima"?

1 Answer 1


It is the dual instrumental case.

Since usually everything has 2 eyes, the Czech noun oko “eye” has kept the old Slavic dual form oči, plural being oka. The Common Slavic language, like other Proto-Indo-European dialects, had three numbers: singular, dual, and plural. Later, most modern Slavic languages lost the dual number, to different extent, only Slovene seems to still keep it fully, in nominal declension, in verb conjugation, and also in personal pronouns. Other modern Slavic languages have kept only remnants of the old dual, oči being on of the few such remnants in Czech.

Other Czech nouns retaining their dual forms are the names of some of the paired body parts:

  • ruce - hands
  • nohy - legs
  • kolena - knees
  • ramena - shoulders
  • uši - ears

Here you can find their declension charts.

If such nouns in their dual form have declinable attributes like possessive pronouns or adjectives, the attributes take their plural feminine forms, and in the instrumental case the suffix is -ýma, not -ými as it would be expected.

Here you can find a summary of the Czech dual with examples.

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    Being pedantic, it is the form derived from the old dual but the plural number. Czech does not have any dual number. It is a form that is used for the plural of certain pair entities, no matter in what amount they come. Dual number would only be used when there are two of them. "pěti obrovskýma očima" Also, the dual-originating forms only appears in some cases of the plural. Commented Mar 18 at 8:41
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    Also, it is worth mentioning that these forms coincide with the Common Czech forms for all nouns and adjectives. School pupils are then being told that these forms are incorrect (nespisovné ) and that they should use the Standard Czech forms (spisovné). This results in them being hesitant to use the dual forms, because they look like those "incorrect" forms they use every day. One could even here this on the TV when some sports experts (sportsmen, non-journalists) make the mistake of not using the dual forms when actually they would use them their casual speech all the time. Commented Mar 18 at 9:05
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    E.g. Standard Czech: "s velkými oky" Common Czech: "s velkýma okama". Commented Mar 18 at 9:07

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