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Sterna is a genus of terns in the bird family Laridae.
Sterna is derived from Old English "stearn" which appears in the poem The Seafarer (1000 years after C.E).

1/ Common tern (Nhàn, Sterna hirundo) 
The Latin for swallow is hirundo, and refers here to the tern's superficial likeness to that unrelated bird, which has a similar light build and long forked tail. This leads to the informal name "sea swallow".

2/ Black-bellied tern (Nhàn bụng đen, Sterna acuticauda)

3/ Roseate tern (Nhàn hồng, Sterna dougallii)

4/ Black-naped tern (Nhàn Xumatra, Sterna sumatrana)