"Magic" versus "magical"

I think with careful speakers/writers, explicitly structurally adjectival magical is usually reserved for metaphoric usages, whereas magic tends to be more literally to do with the "supernatural". So if I were considering the utterances of a careful speaker, I would expect this distinction...

1: "You should read this magic book" (it's a book about magic)
2: "You should read this magical book" (reading it will be a metaphorically enchanting experience)

Note that where the referent is something that often occurs with the "noun-used-as-adjective" form (such as magic trick, lamp, beans, spell, wand, etc.) it usually carries a sense that the target noun has supernatural powers. My careful writer could imply that his book actually had supernatural powers in speech (by placing very heavy stress on the word magic), but in writing it would require rephrasing or help from context to disambiguate that third possible sense.

I suspect that (particularly in casual speech) there may be a tendency to use the shorter adjectival form more often, simply because the "more appropriate" full version sounds a bit highfalutin.

Having said that, there are plenty of established collocations where no literal reference to the supernatural is implied by the short form (magic square, lantern), and some that almost defy categorisation (magic marker, bullet). Those are the ones you just have to learn to get used to.

There is a slight difference between magic and magical.

• magic (adjective) ~ 1. pertaining to magic (n.); used in magic (n.); having the power of magic (n.); as, "a magic wand" and 2. producing extraordinary results, as if by magic (noun) or supernatural means.
• magical (adjective) ~ magic (especially in sense 2 of magic (adj.), defined above): used predicatively as well as attributively, whereas magic (adj.) tends to be attributive alone.

(Webster's New 20th C. Dictionary, Unabridged, 2nd Ed., c.1959)

So, both words may be used attributively, but only magical may be used predicatively.

A number of usage commentators have visited the questions of whether and to what extent magic and magical differ as adjectives. The earliest reference work I have found that addresses these questions is Frank Vizetelly, The Practical Standard Dictionary of the English Language (1922):

magic, a[dj] 1. Of the nature of magic; used in magic; possessing supernatural powers; sorcerous. 2. Magical. 3. Acting like magic. ...

magical a[dj] Pertaining to or produced by magic. Syn[onym]: magic. The adjective magic is applied more commonly to the powers, influences, or practices, while magical is more frequently used of the effects of magic; we speak of magic arts, a magic wand, but of magical effect, a magical result; the magic art of Circe produced magical transformations of her victims. In many cases the choice between the two words is determined by euphony, or, in poetry by meter.

A more detailed discussion appears in Henry Fowler, Modern English Usage (1926):

magic(al), adjectives. ... Magic tends to lose those adjective uses that cannot be viewed as mere attributive uses of the noun. That is, first, it is very seldom used predicatively ; the effect was magical (never magic) ; the ring must be magical (not magic, though must be a magic one is better than magical one). And, secondly, the chief non-predicative use is in assigning a thing to the domain of magic (a magic ring, carpet, spell, crystal ; the magic art), or in distinguishing it from others & so helping its identification (magic lantern, square), rather than in giving its characteristics descriptively (with magical speed ; what a magical transformation) ; this second differentiation, however, is not yet strictly observed.

Fowler thus observes (in 1926) a situation in which use of magic as a predicate modifier and where attributive use typically doesn't extend to "giving [a thing's] characteristics descriptively." Evidently, Fowler expects general descriptive usage of "magic" as an adjective to become more strictly observed in the future than at the time of his writing.

Notably, Ernest Gowers's revised edition of Modern English Usage (1965) retains the first edition's wording verbatim, except that it omits the final nine words ("this second differentiation, however, is not yet strictly observed"). Presumably, Gowers feels that (as of 1965) the situation has resolved itself as Fowler had predicted and strict observation of the second distinction now prevails.

Other writers have made similar claims. For example Bergen Evans & Cornelia Evans, A Dictionary of Contemporary American Usage (1956) offers this assessment:

magic; magical. Of the two adjectives, magical is the more versatile, sine it can be used to describe attributes or characteristics (a magical transformation) and to stand predicatively (The reaction was magical). Magic, on the other hand, is now used chiefly to identify (magic lantern, Magic Flute).

Harry Shaw, Dictionary of Problem Words and Expressions (1975) says this:

magic, magical. As a noun, magic refers to producing results through mysterious influenceor unexplained powers. It involves the control by persons skilled in magic or supernatural agencies and the forces of nature. In view of this meaning, magic seems loosely used and overused to refer to occurrences that might correctly be labeled "unusual," "effective," or "spectacular." "His piano playing was magic" and "When she smiled the effect was magic" are examples of such misuses of a powerfully charged word. As an adjective, magic means much the same as magical, but here again exaggeration is usually apparent: The lovers spent a magical (or magic) night" and "This baritone has a magic (or magical) range to his voice" are examples of overemphasis. Recommendation: use both adjectives sparingly and always place magic before the word it modifies: "magic number," "magic square," "magic lantern," "magic artistry." If this can't be done, use magical.

George Davidson, Chambers Pocket Guide to Good English (1985) [combined snippets, but not the complete entry] has this description:

magic, magical The adjective magic generally means 'pertaining to magic': a magic wand; He rode on a magic carpet. Magical on the other hand, means 'as if caused by magic , enchanting', as in It was a magical experience ; a magical change of character. ...

Merriam-Webster, Webster's Dictionary of English Usage (1989) cites several of the preceding sources and then offers its own assessment of the magic(al) landscape:

magic, magical According to Fowler 1026 the distinguishing features of magic and magical are that (1) magic is almost always used attributively and (2) magic is used literally and in fixed phrases while magical is used with extended meaning. Shaw 1975 objects to figurative uses of magic and magical because he believes they are overused; he also advises using magical when magic cannot be used attributively. Chambers [that is, Davidson] 1985 assigns literal uses to magic and figurative uses to magical. We agree to some extent with Fowler and Shaw but disagree with Chambers. Here is what we found in the evidence we have collected.

The adjective magic is almost exclusively an attributive adjective, partly because the word magic after a linking verb can be construed either as a noun or an adjective. Magical can be either attributive or a predicate adjective, but attributive uses are about three times as common as the others. So nonattributive uses of either word are relatively uncommon. Attributive uses that are part of fixed phrases (as magic carpet, magic square, and magic number) call for magic, not magical.

Both words are used with literal force to refer to the supernatural [Examples omitted.] And both are commonly used with extended meanings, though their connotations may differ. Magic often implies some kind of instant effect, while magical often involves a feeling such as enchantment. These are only tendencies, however, because the figurative uses of the two words overlap quite bit.

Kenneth Wilson, The Columbia Guide to Standard American English (1993) suggests that there is very little separation between how the two words are used as modifiers:

magic (adj. n.), magical (adj.) Magic is primarily an attributive adjective (a magic box), but both magic and magical can appear in predicate use, magical clearly as predicate adjective and magic as either that or a predicate nominative: Her sudden appearance was magic {magical}. We use both words literally (a magic wand, a magical top hat) and figuratively (It was a magic moment; His hold on the audience was magical).

Compared to the other usage commentaries mentioned here, Michael Swan, Practical English Usage, second edition (1995) offers coverage that is broad and general to the point of limited usefulness:

magic and magical Magic is the more common word, and is used in a number of fixed expressions. [Examples:] a magic wand (= a magician's stick) | the magic word | a magic carpet

Magical is sometimes used instead of magic, especially in metaphorical senses like 'mysterious', 'wonderful' or 'exciting'. [Example:] It was a magical experience.

As a side note, I find it interesting that Swann doesn't use the Oxford comma, even though the book is published by Oxford University Press.

Martin Manser, Good Word Guide: The Fast Way to Correct English - Spelling, Punctuation, Grammar and Usage, fifth edition (2003) offers a more detailed assessment of the two words:

magic or magical? The adjective magic is more closely related to the art or practice of magic than magical, which is used in the wider sense of 'enchanting' | a magic wand | a magic potion | a magic spell | a magical experience | the magical world of make-believe.

The two adjectives are virtually interchangeable in many contexts, although magic is retained in certain fixed expressions such as: | magic carpet | magic lantern, etc., and magical is sometimes preferred for things that happen as if by magic: | a magical transformation. Magic, but not magical, is also used in informal contexts to mean 'wonderful': | The holiday was magic!

I have no idea what information Manser was relying on for that last observation, but a Google Books search finds just one confirmed match (other than Manser's own book for "holiday was magic"—"That cycling holiday was magic for me and Elsie..." (2016)—but seven for "holiday was magical" over the years 1982–2017 (not counting a 2001 instance of "To me, Billie Holiday was magical").

Simon Heffer, Simply English: An A to Z of Avoidable Errors (2014) resuscitates Davidson's argument that the difference in usage between the two terms is that magic applies to literal situations magical to figurative ones:

Magic and magical A magic moment is when something illusory or supernatural appears to have happened. A magical moment is when it is quire obvious that something illusory or supernatural has not happened, but the ambience of the occasion could cause one to think that it might. The adjective in -ic is literal; the one in -ical metaphorical, suggesting that something has the properties or likeness of magic. The dictionary defines magical as 'of or relating to magic' in the first definition, but a second one, almost as old and now more idiomatic, is 'resembling magic in action or effect; enchanting'.

This is precisely the component of Davidson's treatment of the two words that Webster's Dictionary of English Usage flatly rejected back in 1989.

For truly in-depth coverage of how English speakers and writers use magic and magical, easily the most impressive source I came across was Mark Kaunisto, Variation and Change in the Lexicon: A Corpus-Based Analysis of Adjectives in English Ending in -ic and -ical (2007). Kaunisto devotes a 30-page chapter, titled "From Supernatural Powers to Exciting Football Games: Magic/Magical," to the word pair in question. He begins by observing that magic and magical seems to invite a greater level of caution among prescriptivist commentators than most other differentiable -ic/-cal adjective pairs do:

Although magic/magical is usually listed among those -ic/-ical pairs subject to semantic differentiation, it is also that pair among the ones studied with which writers of usage manuals tend to lean towards descriptivism rather than taking a firm prescriptivist stance. It is this adjective pair that writers of usage manuals would most readily admit as showing a degree of semantic overlap, even interchangeability, of the two forms, while maintaining that more or less clear distinctions of usage can nevertheless be perceived. As with other -ic/-ical pairs in present-day English, one can find instances of slips or inconsistencies in the use of magic and magical by one and the same writer, ...

Ultimately, Kaunisto seems to be inclined to interpret the difference in usage between magic and magical as following roughly along the lines of the difference in usage between electric and electrical:

It would seem that the semantic aspects of the collocating words play a role in the choice of the adjective: the more "remote" words representing the classifying sense 'having to do with magic', e.g. knowledge, appear more often with magical, whereas the words denoting more "immediate", concrete or visible things, such as actions of conjuring or enchanted objects, tend to select the shorter form of the adjective. In phrases denoting the idea of the phenomenon itself, magical is used more often, which contrasts with the assumption that a closer semantic connection with the basic or original sense of the adjective would generally show as a preference for the -ic form. It can be argued then that the selection of either magic or magical according to the head word follows the lines of concrete versus abstract or immediate versus remote. As was seen earlier, such a distinction could also be seen to some extent with the pair electric/electrical, where the longer form is preferred ion senses with a more remote connection with electricity, as in electrical engineering. In the sense 'powered by electricity', the selection of the adjective was governed by the head word through an opposition of specific versus general (electric kettle vs. electrical appliances). This type of drastic distinction, however, cannot be observed in the case of magic/magical with head words such as artefacts, items, objects, etc., with which both forms are found in the material studied, in spite of the head word clearly signifying concrete things[.]

Kaunisto devotes considerable space to instances of magic/magical as a synonym for enchanting, wonderful, excellent, and special. When used for this purpose, the two words seem to be very nearly interchangeable, especially in British English. Kaunisto also provides a couple of interesting charts—one consisting of adjective occurrences of magic and magical in Literature Online for the years 1850–1903, in which magic appears 178 times and magical 64 times, and the other consisting of adjective occurrences of the same two words in the [London] Daily Telegraph during 1995, in which magic appears 277 times and magical 280 times. Clearly, magical things are happening at about the same rate as magic things these days—and the great majority of the magical instances in 1995 involved situations where the adjective was used to signify (according to Kaunisto's assessment) "'enchantingly beautiful', 'wonderful' 'thrilling'"; in this subcategory of usage the tally was 45 for magic and 196 for magical, up from 16 for magic and 11 for magical in the 1850–1903 period.

Kaunisto's conclusion is worth considering, too:

Considering the results concerning the use of the adjectives in the corpora in general, there is perhaps less interchangeability today than one would expect from the comments referred to in the introductory paragraphs of this chapter. One feature that is often stressed in usage manuals is the "freer" or less restricted use of magical in both attributive and predicative positions in the sentence. When one examines the numbers of predicative uses of magic and magical, a difference in favour of magical can be observed, but the difference is perhaps not as striking as one would have expected. This itself may not be entirely surprising, because usage manuals have a tendency to pay attention to questions of acceptability, which are not necessarily directly reflected in actual frequencies of use.

As far as possible future developments in the use of magic/magical are concerned, perhaps the most crucial meaning where changes are likely is the descriptive sense 'enchanting'. The notion of approval, which is increasingly signalled through the word magic, may be linked more closely to the use of both adjective forms in this sense. Given the direction of change in most semantically differentiated -ic/-ical pairs, one might assume that magic eventually becomes the more frequent form in the descriptive sense as well, as in the case of electric/electrical, and that the choice between the two forms will be governed even more strongly by the collocating words.

According to this assessment, although magical has made tremendous headway against magic on the "enchantingly beautiful/wonderful/thrilling" front since the early 1900s, magic is likely to become more and more common in both predicate positions and attributive positions where the adjective is functions figuratively or descriptively. Someday, language and usage mavens may come to recognize how far ahead of his time Ben E. King was when he sang (back in 1960) about "This Magic Moment."