"protoplasm, organic substance forming the essential constituent of cells," 1870, from cyto- "cell" + -plasm. Related: Cytoplasmic.

crystalline base which is one of the constituents of nucleic acids, 1894, from German cytosin (1894), from cyto- "cell" + -ose + chemical suffix -ine (2). "The name cytosine (due to Kossel and Neumann) is misleading. Cytosine is not, like adenosine and guanosine, a nucleoside but the sugar-free base." [Flood]

"poisonous to cells," 1902, from cyto- + toxic. Related: Cytotoxin (1900); cytotoxicity.

the common title of the emperor of Russia, 1550s, from Russian tsar, from Old Slavic tsesari, from Gothic kaisar, from Greek kaisar, from Latin Caesar. First adopted by Russian emperor Ivan IV, 1547.

The spelling with cz- is against the usage of all Slavonic languages; the word was so spelt by Herberstein, Rerum Moscovit. Commentarii, 1549, the chief early source of knowledge as to Russia in Western Europe, whence it passed into the Western Languages generally; in some of these it is now old-fashioned; the usual Ger. form is now zar; French adopted tsar during the 19th c. This also became frequent in English towards the end of that century, having been adopted by the Times newspaper as the most suitable English spelling. [OED]

The Germanic form of the word also is the source of Finnish keisari, Estonian keisar. The transferred sense of "person with dictatorial powers" is first recorded 1866, American English, initially in reference to President Andrew Johnson. The fem. czarina is 1717, from Italian czarina, from Ger. Zarin, fem. of Zar "czar." The Russian fem. form is tsaritsa. His son is tsarevitch, his daughter is tsarevna.

"member of the westernmost branch of the Slavic people," the native name for Bohemians (and including the Moravians), 1848, from Czech český "Bohemian, Czech," which is said to be from the name of an ancestral chief (who is mentioned in English by 1837), but perhaps from a source akin to Czech četa "army." Meaning "the Czech language" and use as an adjective both are also from 1848. Sometimes in early use, Tshekh, from French.

Central European nation from 1919-1992, from Czecho-, Latinized combining form of Czech + Slovakia (see Slovak). Related: Czechoslovak; Czechoslovakian. Since the breakup the western part has been known in English as the Czech Republic or Czechia.