In words physical, mathematical, chemical, etc. Does the -cal suffix mean a matter of or belonging to, or maybe concerning?
With what words can we use it and why do some words change when we add -cal? Wgat I mean by change is:
There is no -cal suffix. There are some words with an -ic suffix and others with -ical. Usually they mean the same thing.
From the OED:
-ic, suffix. Forms: (formerly -ick, ik(e, -ique), primarily forming adjs., many of which are used as ns. The latter have also the form -ics.
Etymologically, the OED comments:
In adjs., immediately representing French -ique, < Latin -ic-us, of Latin origin, as in cīvic-us, classic-us, public-us, domestic-us, aquātic-us, or < Greek -ικ-ός, as in κωμικ-ός cōmic-us, γραμματικ-ός grammatic-us, ποιητικ-ός poētic-us. This was in Greek one of the commonest of suffixes, forming adjs., with the sense ‘after the manner of’, ‘of the nature of’, ‘pertaining to’, ‘of’. Its use in Latin was much more restricted,
Adverbially:
A few adjs. in -ic form advs. in -icly, as publicly, franticly, heroicly; but the adv. is usually in -ically suffix, from the secondary adj. in -ical suffix.
On -ical, the OED says:
Sometimes forming an adjective from a noun in -ic, as music, musical, but more frequently a secondary adjective, as comic, comical, historic, historical. Its origin appears to have been the formation in late Latin of adjectives in -ālis on nouns in -ic-us, or in -icē... In French, adjectives of this type are few, and mostly taken directly from Latin formations, as chirurgical, clérical, grammatical, médical, etc. But in English they are exceedingly numerous...
It elaborates on the -ic/-ical distinction:
Many adjectives have a form both in -ic and -ical, and in such cases that in -ical is usually the earlier and that more used. Often also the form in -ic is restricted to the sense ‘of’ or ‘of the nature of’ the subject in question, while that in -ical has wider or more transferred senses, including that of ‘practically connected’ or ‘dealing with’ the subject. Cf. ‘economic science’, ‘an economical wife’, ‘prophetic words’, ‘prophetical studies’, ‘a comic song’, ‘a comical incident’, ‘the tragic muse’, ‘his tragical fate’. A historic book is one mentioned or famous in history, a historical treatise contains or deals with history.
The conclusion is:
But in many cases this distinction is, from the nature of the subject, difficult to maintain, or entirely inappreciable.
First, you are correct in assuming that -ical means a matter of or belonging to. All definitions you suggested are more or less correct; it simply means related to the field of, for example mathematical, meaning related to the field of mathematics.
The change to which you are referring happens because these words are derived from Latin and Greek roots; mathematics from "mathema" and chemistry from "khemia" (these are English approximations of the pronunciation). When modifying these words with suffixes or prefixes, the root is the only part of the word that is always preserved.
The -cal suffix may be used with most words ending in -ic or, more rarely, -ry/-y. See the following examples:
Electric - Electrical
Numeric - Numerical
Rhetoric - Rhetorical
History - Historical
Anatomy - Anatomical
Note that these are all fields or topics. This rule does not extend to other words, with a few exceptions. Examples of words that cannot have -ical added as a suffix:
Moronic - Moronical
Icelandic - Icelandical
Sophistry - Sophistical
To add to the confusion, there are some -ical words that are technically valid (dictionaries have entries for them), but are so rare that they are likely to get a few strange looks from people if you use them:
Atomic - Atomical
Ironic - Ironical
Rhythmic - Rhythmical
In nearly every instance of this suffix, you will see it used for fields of study. There are a few commonly used exceptions to this rule:
Allegorical
Hypothetical
Theoretical
There are even more words beyond these that do not take a -ical suffix, but an -al suffix to mean "related to," but these are beyond the scope of this question.
