RNA secondary structure

The secondary structure of a RNA refers to the basepairing interactions within a single molecule or set of interacting molecules of RNA. Some nucleotides of a RNA molecule can pair with each other via hydrogen bonds and form a stable structure.

Hairpin loop
A hairpin loop is a structure in which the pairing of intramolecular base pairs occurs. It takes place when two regions of the same molecule, usually forming a palindrome, form pairs to constitute a double helix ending in a loop unpaired.