Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
concentĭo, ōnis, f. [concino], a singing together, harmony (very rare): clarissima (catervae), Cic. Sest. 55, 118; id. Tim. 8, 24; App. de Mundo, p. 71, 20.