Individually in succession; one at a time.(adverb)
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Use "one by one" in a sentence
"There were the specific mysteries, the Santa Clauses and the Tooth Fairies, debunked one by one with a kind of bittersweet pride."
"So one by one the Habitas artisans and apprentices disappeared until the establishment consisted of Richard and Senhor Tomas Habitas himself."
"These extraordinary foreign figures, each with his complete set of crimes, horrible customs and ‘minor peculiarities,’ march one by one from the dark wings of Barbarism up to the bright footlights of Civilisation."