a suffix occurring in loanwords from Latin, where it formed feminine nouns or adjectives corresponding to agent nouns ending in -tor (Bellatrix). On this model, -trix is used in English to form feminine nouns (aviatrix; executrix) and geometrical terms denoting straight lines (directrix).
Origin of -trix
< Latin -trīx, stem -trīc-
A suffix borrowed directly from Latin, -trix has been used since the 15th century on feminine agent nouns that correspond to a masculine (in Latin) or generic (in English) agent noun ending in -tor: aviator, aviatrix; legislator, legislatrix; orator, oratrix. Most nouns in -trix have dropped from general use, so that terms like aviatrix, benefactrix, legislatrix, oratrix, and proprietrix occur rarely or not at all in present-day English. The forms in -tor are applied to both men and women: Her sister is the proprietor of a new restaurant. When relevant, sex is specified with the generic term: Amelia Earhart was a pioneer woman aviator. Legal documents still use administratrix, executrix, inheritrix, and the like, but these forms too are giving way to the -tor forms. See also -enne, -ess, -ette.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
suffix forming nouns
indicating a feminine agent, corresponding to nouns ending in -torexecutrix
Word Origin for -trix
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
fem. agential suffix, from Latin, corresponding to masc. -tor.
Online Etymology Dictionary, © 2010 Douglas Harper