осока

Russian

Russian Wikipedia has an article on:

осока

Per Vasmer, possibly cognate with сечь (sečʹ, “to cut, to chop”) (1sg. секу́ (sekú)). Others propose a connection with Proto-Indo-European *h₂еḱ- (“sharp”) (whence Russian о́стрый (óstryj)), relating the term to Lithuanian ašakà (“fishbone”), also ãšaka.

осо́ка • (osóka) f inan (genitive осо́ки, nominative plural осо́ки, genitive plural осо́к)

Declension of осо́ка (inan fem-form velar-stem accent-a)

	singular	plural
nominative	осо́ка osóka	осо́ки osóki
genitive	осо́ки osóki	осо́к osók
dative	осо́ке osóke	осо́кам osókam
accusative	осо́ку osóku	осо́ки osóki
instrumental	осо́кой, осо́кою osókoj, osókoju	осо́ками osókami
prepositional	осо́ке osóke	осо́ках osókax

Ukrainian Wikipedia has an article on:

осока

Wikipedia ^uk

Per Vasmer, possibly cognate with сікти́ (siktý, “to cut, to chop”). Others propose a connection with Proto-Indo-European *h₂еḱ- (“sharp”) (whence Ukrainian го́стрий (hóstryj)), relating the term to Lithuanian ašakà (“fishbone”), also ãšaka.

осока́ • (osoká) f inan (genitive осоки́, nominative plural осоки́, genitive plural осо́к)

Declension of осока́ (inan hard fem-form accent-b)

Bilodid, I. K., editor (1970–1980), “осока”, in Словник української мови: в 11 т. [Dictionary of the Ukrainian Language: in 11 vols] (in Ukrainian), Kyiv: Naukova Dumka
Shyrokov, V. A., editor (2010–2023), “осока”, in Словник української мови: у 20 т. [Dictionary of the Ukrainian Language: in 20 vols] (in Ukrainian), volumes 1–14 (а – префере́нція), Kyiv: Naukova Dumka; Ukrainian Lingua-Information Fund, →ISBN
Ukrainian Lingua-Information Fund (2001–2024) “Словники України” online [Dictionaries of Ukraine online]‎^[1] (in Ukrainian)