A worker who is paid according to the number of units of work produced.(noun)
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Use "pieceworker" in a sentence
"Also une pigiste = pieceworker, typesetter, freelance journalist who is paid by the line"
"The pieceworker with more satisfaction to himself and profit to the world will produce far more than he would turn out under a daily wage if his earnings are thereby increased."
"The manager's term of employment is longer, but the professional pieceworker, such as I am when I write this article, has usually no contracted term, and is only paid for actual work done."