Avialae

Avialae is a term for birds and their immediate extinct ancestors. It is a clade of dinosaurs containing their only living representatives (birds) and whatever coelurosaurs are regarded as their ancestors. There are two ways it can be defined:
Definition by physical characters.
Avialae is defined as a clade based on physical characteristics. Jacques Gauthier named Avialae in 1986 as "all dinosaurs that possessed feathered wings used in flapping flight, and the birds that descended from them".
Branch-based definition.
Several other authors use a similar, but branch-based, definition: "all theropods closer to birds than to Deinonychus".