Charadrius is a genus of plovers, a group of wading birds in the family Charadriidae, in the order Charadriiformes. 

1/ Common ringed plover or ringed plover (Charadrius hiaticula)

The two below species are moved to the genus Thinornis.

1/ Long-billed plover (Choi choi lớn, Charadrius placidus)

2/ Little ringed plover (Choi choi nhỏ, Charadrius dubius) 
The specific dubius is Latin for doubtful, since Sonnerat, writing in 1776, thought this bird might be just a variant of common ringed plover.

Charadrius comes from the Ancient Greek kharadrios, meaning a bird found in river valleys or ravines ((kharadra) being ravine), and was later adopted into Late Latin. The Latin word charadrius described a yellowish bird mentioned in the Vulgate Bible.