Princeton's WordNet

1. one by one, one after another, one at a time(adverb)

   in single file

   "the prisoners came out one by one"

2. by the piece, one by one(adverb)

   one piece at a time

   "she sold the plates by the piece"

3. individually, separately, singly, severally, one by one, on an individual basis(adverb)

   apart from others

   "taken individually, the rooms were, in fact, square"; "the fine points are treated singly"

Wiktionary

1. one by one(Adverb)

   Individually in succession; one at a time.

• een vir een, afsonderlikAfrikaans
• واحِدا تِلْو الآخَرArabic
• един по единBulgarian
• um a umPortuguese (BR)
• postupněCzech
• Stück für StückGerman
• en efter enDanish
• ένας έναςGreek
• de uno en uno, uno tras otroSpanish
• ükshaavalEstonian
• یکی یکیFarsi
• yksi kerrallaanFinnish
• un par unFrench
• אֶחָד אֶחָדHebrew
• एक-एक कर केHindi
• jedan po jedanCroatian
• egyenkéntHungarian
• satu demi satuIndonesian
• einn aföðrumIcelandic
• uno per unoItalian
• １つずつJapanese
• 하나씩, 차례로Korean
• vienas po kitoLithuanian
• viens pēc otra; cits pēc citaLatvian
• satu demi satuMalay
• één voor éénDutch
• én etter én, én om gangenNorwegian
• jeden po drugimPolish
• یکی یکیPersian
• يو يوPashto
• um a umPortuguese
• unul câte unulRomanian
• один за другимRussian
• postupneSlovak
• drug za drugimSlovenian
• jedan po jedanSerbian
• en efter enSwedish
• ทีละคนThai
• birer birerTurkish
• 一個一個地Chinese (Trad.)
• один за однимUkrainian
• باري باري، ايک ايک کرکےUrdu
• lần lượtVietnamese
• 一个一个地Chinese (Simp.)