Lowercase ɐ (in two story form) is used in the International Phonetic Alphabet to identify the near-open central vowel. A variant, turned alpha, ɒ, is also used in the IPA as the open back rounded vowel.
It was used in the 18th century by Edward Lhuyd and William Pryce as phonetic character for the Cornish language. In their books, both Ɐ and ɐ have been used.  It was used in the 19th century by Charles Sanders Peirce as a logical symbol for 'un-American' ("unamerican").
The symbol ∀ has the same shape of a capital turned A, sans serif. It is used to represent universal quantification in predicate logic. When it appears in a formula together with a predicate variable, they are referred to as a universal quantifier. In traffic engineering it is used to represent flow, the number of units (vehicles) passing a point in a unit of time.
Ɐ is encoded in Unicode at U+2C6F Ɐ latin capital letter turned a (HTML:
Ɐ) in the block Latin Extended-C, though very few fonts support it as of 2008, and ɐ is encoded in Unicode at U+0250 ɐ latin small letter turned a (HTML:
ɐ) in the block IPA Extensions.
The similar turned alphas are at U+2C70 Ɒ latin capital letter turned alpha (HTML:
Ɒ capital), and at U+0252 ɒ latin small letter turned alpha (HTML:
The mathematical symbol ∀ is encoded at U+2200 ∀ for all (HTML:
∀), in the mathematical operators and symbols in Unicode, and only in a sans-serif form.
The Symbol font includes ∀ at position 34 (which would produce the quotation mark in ASCII and Unicode).
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Letter A with diacritics