onebyone
adverbUK /ˌwʌn baɪ ˈwʌn/
US /ˌwʌn baɪ ˈwʌn/
One by one means doing things one at a time, not all together.
The teacher called the children one by one to get their books.
RELATED WORDS
OTHER MEANINGS
2. Slowly and in order, with each thing finished before the next begins.
He solved the puzzle one by one until it was done.
3. Each person or thing taking their turn in a line or group.
The students walked into the room one by one.
4. Done in small steps rather than all at once.
She learned the new words one by one.