1. In single file
   "the prisoners came out one by one"
   - one after another, one at a time 
2. One piece at a time
   - by the piece 
3. Apart from others
   - individually, separately, singly, severally, on an individual basis

Encyclopedia: One by one

• American Indian Day
• American ivy
• American kestrel
• American Labor Party
• American lady crab
• American language
• American larch
• American laurel
• American Legion
• American leishmaniasis
• American licorice
• American lime
• American liquorice
• American lobster
• American lotus
• American magpie
• American maidenhair fern
• American marten
• American mastodon
• American mastodont
• American merganser
• American mink
• American mistletoe
• American mountain ash
• American oil palm