First letter of the Greek alphabet, α.
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al·pha 'al-fə n
1) the 1st letter of the Greek alphabet symbol À or à
2) ALPHA PARTICLE
3) ALPHA WAVE
1) of or relating to one of two or more closely related chemical substances <the alpha chain of hemoglobin> <à-yohimbine> used somewhat arbitrarily to specify ordinal relationship or a particular physical form, esp. one that is allotropic, isomeric, stereoisomeric, or sometimes polymeric (as in à-D-glucose)
2) closest in position in the structure of an organic molecule to a particular group or atom also occurring at or having a structure characterized by such a position <à-substitution>
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al·pha (alґfə) [A, α] the first letter of the Greek alphabet. See also α-.Medical dictionary. 2011.