The term secondary olfactory areas refers to a group of substructures of the endbrain, which were defined on the basis of connectivity as belonging to the functionally defined olfactory system. The structures to which it applied depended on whether an author regarded the primary olfactory area to be the layered, cortical-like main olfactory bulb or more central structures that receive axonal fibers from the olfactory bulbs ( Anthoney-1994 ). From the early 1900s to the 1940s, 'secondary olfactory area' was used about seven times more frequently than 'primary olfactory area' ( Ngram-2019 ). From then to 2019 its use gradually fell to about one sixth that of 'primary olfactory area', and the use of both fell to less than one-eighth that of a new term coined in the 1960s: 'primary olfactory cortex' ( Helwany-2023 Ngram-2019 ). The composition of' primary olfactory cortex' ( Price-1990 ) makes that term a synonym of olfactory cortex.( NeuroNames ). Updated 9 Jun 2024.