No,there isn't a singular 'mathematic' - but there is an adjective, as an alternative to 'mathematical'.

In any case it's not really correct to term either math or maths as abbreviations, or it would properly need to have a full stop ('period') after it. They are new words based on abbreviating, and as such they can be spelt however the relevant linguistic community prefer.
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But is it acceptable for Yanks to use the term "pommy"? How do Australians feel about that?