One of the ways to form an adjective is to add the suffix ~ic or ~ical. There is no clear rule about when to use which. As a rule of thumb, many of the older nouns have the ~ical adjective, while most of the newer ones have ~ic suffix.
The suffix ~ic or ~ical means “connected with” in adjectives and nouns or refers to “that performs the action mentioned” in adjectives. Especially, nouns that end with “logy” takes “logical” as the suffix when becoming an adjective. The suffix is derived from French ~ique (or Latin ~icus or Greek ~ikos).
OK, while I say that older forms are ~ical and newer words take ~ic, there are so many words that take both forms. This post aims to shed light into the pair of words that have different meaning with ~ic and ~ical.
Classic vs Classical
Classic refers to a conventional or traditional style. Anything classic is famous.
Classical relates to the ancient Greek and Roman world and especially to its literature, art, architecture, or ideals. It also is concerned with or giving instruction in the humanities, the fine arts, and the broad aspects of science. Classical music is serious music.
Comic vs comical
Comic usually denotes artistic comedy and comical means funny. The latter is a rather old-fashioned word.
Economic vs Economical
Economic broadly refers to the study of economics or the economy of a country. Economical is the prudent use of resources. It means not wasting money.
Electric vs Electrical
With more general words, we use electrical; with specific machines that run on electricity, we use electric. To refer to something fully excited, we use electric, not electrical.
Historic vs Historical
Historic is used to denote something historically important and achievements of highest degree, the moments that create history. Historical is connected with the study of history or really existing in history.
(Compare with economic which is used to refer to the study of economics, while historical, not historic, is connected with the study of history. There is no logic here, I tell you.)
Lyric vs lyrical
Lyric refers to poetry and lyrical is poetic.
Magic vs magical
Magic is a more common word and is used in general expression. Magical may sometimes substitute magic; however, magical is used in metaphorical senses to mean mysterious, wonderful, exciting.
Politic vs political
Politic is shrewdly tactful and is characterized by shrewdness in managing, contriving, or dealing. Political is connected with politics.
(Now, you have “political and historical” vs “economic”.)
1. Practical English Usage by Michael Swan.
2. Merriam-Webster’s Collegiate Dictionary, 11th edition.