in vain, to no avail, for nothing · mistakenly, making a mistake (used to indicate someone ought not to do/think/etc. something, or to express the sentiment that it's too bad that they do)
eş: напрасно, тщетно, безуспешно, безрезультатно, бесполезно, без толку
köken: From Old East Slavic *зьрѧ (*zĭrę), adverbial participle of зреть, originally “idly looking”.
aile: зря́шный, почём зря, зряпла́та
Зря мы стара́лись. Всё равно́ никто́ не оцени́л.
Э́то ты зря.
Я не ду́маю, что хорошо́ владе́ю ру́сским языко́м. — А зря.
köken: Uncertain. The word does not occur in Middle Persian writings, except possibly in the Dēnkard, a 10th-century compendium, where it can be interpreted as "nihility"; whence it would be inherited from Middle Persian [Book Pahlavi needed] (pwc /pūč/). The word became widespread in Iranian varieties first in the fifteenth century onward, but existed before it. Possibly from the onomatopoetic…
vain (overly concerned with one's appearance or reputation) · futile, vain (having no chance of success)
çekim: karşılaştırma fåfängare · üstünlük fåfängast
köken: From Old Swedish fafænger, equivalent to past participle of få (“few”) + få (“receive”), thus originally "[which] received little". Compare etymology of eldfängd and befängd. Attested since the mid-14th century in the sense "futile". Compare Norwegian Nynorsk fåfengd.