(adjective)
relating to the normal or common language used by people, especially when contrasted with cultured or literary language, such as in context of the naming of plants and animals in common speech as opposed to scientific classification (Latin);
e.g. Each diagram referred to the organism by its vernacular name as well as its scientific title.
(adjective)
characteristic of a particular place or time period, especially in context of architecture being of a common and functional style;
e.g. This district of the city primarily has vernacular buildings with office spaces.
(noun)
a language or mode of expression that is in ordinary use by a particular country or group of people, as opposed to being foreign or formal;
e.g. She spoke the vernacular of the people so that she could better connect with her audiences.
(noun)
the terminology and other modes of expression used by a particular group of people, especially those engaged in some specific activity;
e.g. He is familiar with the vernacular of the sport since he has been playing it for many years.