Agreed. I see they use "matrices" as the plural of "matrix" (eg, "expectancy matrices" in http://fivethirtyeight.com/features/nine-managerial-decisions-that-hel

Agreed. I see they use "matrices" as the plural of "matrix" (eg, "expectancy matrices" in http://fivethirtyeight.com/features/nine-managerial-decisions-that-helped-decide-game-2-of-the-nlcs/ http://fivethirtyeight.com/features/nine-managerial-decision... ) when those not familiar with mathematics would likely use "matrixes." Examples of matrixes include: VMWare - http://partnerweb.vmware.com/comp_guide2/sim/interop_matrix.php http://partnerweb.vmware.com/comp_guide2/sim/interop_matrix.... Reference to the movie "The Matrix" ("How many Matrixes were there?"; see also the comments) - http://scifi.stackexchange.com/questions/109115/how-many-matrixes-were-there http://scifi.stackexchange.com/questions/109115/how-many-mat... "Evaluation Planning: Models and Matrixes" - http://www.iste.org/docs/pdfs/evalplan http://www.iste.org/docs/pdfs/evalplan Of course, in math the plural is matrices. Then again, in biology the plural is genera. They also have no problem using "cacti" at http://fivethirtyeight.com/features/unlocking-the-mystery-of-the-chile-pepper-on-a-burrito-tour-of-new-mexico/ http://fivethirtyeight.com/features/unlocking-the-mystery-of... instead of "cactuses", even though both are acceptable. Compare the ngram distribution for genuses/genera at https://books.google.com/ngrams/graph?content=genera%2Cgenuses&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cgenera%3B%2Cc0%3B.t1%3B%2Cgenuses%3B%2Cc0 https://books.google.com/ngrams/graph?content=genera%2Cgenus... with almost no hits for 'genuses' vs. cactuses/cacti at cactuses,cacti .