α 

https://doi.org/10.1351/goldbook.08143
  1. Designation applied to the carbon to which a functional group is attached.
  2. In carbohydrate nomenclature, a stereochemical designation of the configuration at the anomeric carbon.
  3. Parameter in a Brønsted relation expressing the sensitivity of the rate of protonation to acidity.
  4. Parameter in Leffler’s relation expressing the sensitivity of changes in Gibbs activation energy to changes in overall Gibbs energy for an elementary reaction.
Source:
PAC, 2022, 94, 353. 'Glossary of terms used in physical organic chemistry (IUPAC Recommendations 2021)' on page 368 (https://doi.org/10.1515/pac-2018-1010)