/ˈsɛk ənˌdɛr I ˈstrʌk tʃər/

noun

The three dimensional structure of a local segment of a molecule due to its hydrogen bonding pattern. The secondary structure of a nucleic acid would refer to base pairing interactions. Secondary structure in proteins refers to the three dimensional form of a local segment of a protein due to its pattern of hydrogen bonding (alpha helix or beta pleated sheet).

Latin, from secundārius & structūra