# Suffixes -ic and -al: meaning? **URL:** \ **Category:** Factual Questions\ **Created:** [July 17, 2007, 7:31pm UTC](https://boards.straightdope.com/t/suffixes-ic-and-al-meaning/412171 "2007-07-17T19:31:25Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [July 17, 2007, 7:31pm UTC](https://boards.straightdope.com/t/suffixes-ic-and-al-meaning/412171/1 "2007-07-17T19:31:25Z")
How do these change a word? I vaguely recall -ic is preferred as a noun, -al for an adjective. I haven’t been able to find a source on my own, as Google (at least my searching thereof) results are either too vague or related to computers. An example sentence: Volcanism is involved in the creation of geolog\*\*-ic\*\*/ **-cal** features. Does it make a difference? Thanks, Rhythm ---
**Author:** ![FatBaldGuy](https://avatars.discourse-cdn.com/v4/letter/f/ecd19e/32.png) [@FatBaldGuy](https://boards.straightdope.com/u/FatBaldGuy)\ **Post date:** [July 17, 2007, 8:07pm UTC](https://boards.straightdope.com/t/suffixes-ic-and-al-meaning/412171/2 "2007-07-17T20:07:24Z")
In general both -ic and -al are used to form adjectives. In your example, both geologic and geological are adjectives based on the noun geology. I don’t know of any rule where one or the other has any specific meaning. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [July 17, 2007, 8:38pm UTC](https://boards.straightdope.com/t/suffixes-ic-and-al-meaning/412171/3 "2007-07-17T20:38:10Z")
For adjectives: -ic: of, having to do with; like, having the nature if, characteristic of; produced by, caused by; producing, causing; consisting of, containing, forming; having, showing, affected by… -al: of, like, or suitable for… -ical: sometimes having special or differentiated meanings that the corresponding _-ic_ forms do not have (e.g. economic/economical)… For nouns, see your friendly neighborhood dictionary, whence the above came.