-al 1suff. Of, relating to, or characterized by: parental.[Middle English, from Old French, from Latin -?lis, adj. suff.]-al 2suff. Action; process: retrieval.[Middle English -aille, from Old French, from Latin -?lia, from neuter pl. of -?lis.]-al 3suff. Aldehyde: citronellal.[From al(dehyde).]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.-al suffix forming adjectives of; related to; connected with: functional; sectional; tonal. [from Latin -?lis]-al suffix forming nouns the act or process of doing what is indicated by the verb stem: rebuttal; recital; renewal. [via Old French -aille, -ail, from Latin -?lia, neuter plural used as substantive, from -?lis -al1]-al suffix forming nouns 1. indicating an aldehyde: ethanal. 2. (Pharmacology) indicating a pharmaceutical product: phenobarbital. [shortened from aldehyde]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014al- var. of ad- before l: allure. -al1 , a suffix with the general sense ?of the kind of, pertaining to, having the form or character of? that named by the stem, occurring in loanwords from Latin (autumnal; natural; pastoral), and productive in English on the Latin model, usu. with bases of Latin origin (accidental; seasonal; tribal). Compare -ical, -ar 1, -ial. [