To the definitions already published I add that 'a' is also a preposition, an area symbol, or the prefix for atto ("factor of 10 8315;¹ 8312;"); and 'A' is the letter that in biochemistry represents adenine and alanine, is the symbol of the ampere , is the equivalent to decimal 10 in bases greater than 10, or the musical note in Anglo-Saxon notation.
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