if and only if

English

if and only if

(logic, mathematics) Is equivalent to; implies and is implied by; is true and false in the same cases as.
A rectangle is a square if and only if all four of its sides have the same length.
An integer is even if and only if its square is also even.

implies and is implied by

Arabic: شَرْطَ أَنّ‎ (šarṭa ʾann), فَقَط إِذَا‎ (faqaṭ ʾiḏā), شَرِيطَةً أَنَّ‎ (šarīṭatan ʾanna), فَقَط فِي حَالَة‎ (faqaṭ fī ḥāla)
Egyptian Arabic: بشرط إن‎ (bešarṭ ʾenn), بس لو‎ (bass law)
Basque: baldin eta soilik baldin
Catalan: si i només si
Chinese:
Mandarin: 若且唯若 (ruòqiěwéiruò)
Czech: právě tehdy, když
Danish: hvis og kun hvis
Dutch: dan en slechts dan als (Netherlands), als en slechts als (Belgium)
Esperanto: se kaj nur se
Finnish: jos ja vain jos
French: si et seulement si (fr)
German: genau dann, wenn, dann und nur dann, wenn
Greek: αν και μόνο αν (an kai móno an)
Hebrew: אם ורק אם‎ (he) (im ve-rak im)

Hungarian: akkor, és csakis akkor, ha
Icelandic: ef og aðeins ef, þá og því aðeins að
Irish: is gá agus is leor
Italian: se e solo se
Lithuanian: tada ir tik tada
Persian: اگر و فقط اگر‎ (agar va faqat agar)
Polish: wtedy i tylko wtedy
Portuguese: se e somente se
Romanian: dacă și numai dacă
Russian: тогда́ и то́лько тогда́(, когда́ ...) (togdá i tólʹko togdá(, kogdá ...))
Slovene: če in samo če
Spanish: si y sólo si (es)
Swedish: om och endast om (sv)
Thai: ก็ต่อเมื่อ