-ales suffix forming plural proper nouns denoting plants belonging to an order: Rosales; Filicales. [New Latin, from Latin, plural of -?lis -al1]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014-ales a suffix of names of plant orders in botany: Cycadales. [