The correct way to use this word as an adjective with an indefinite article (a or an) is "a special." You can discern whether to use 'a' or 'an' before a noun or adjective by noting the sound that the word starts with. If a word starts with a consonant, its proper indefinite article would be 'a,' such as "a car" or "a movie." Conversely, if a word starts with a vowel, its proper indefinite article would be 'an,' like "an octopus" or "an apple." The exception to this rule applies to words that sound like they begin with a vowel, even though their spelling begins with a consonant. For example, you would say "an hour" instead of "a hour" because the 'h' in 'hours' is silent.
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