Terns are in the family Sternidae. Their close relationship to gulls in indicated by the fact that they were previously in the family of Laridae or gulls. The genera and species in the family Sternidae are as follows (excluding the Noddys described elsewhere):

Genus Onychoprion - "brown-backed" terns
Grey-backed Tern Onychoprion lunata
Bridled Tern Onychoprion anaethetus
Sooty Tern Onychoprion fuscata
Aleutian Tern Onychoprion aleutica
Genus Sternula - little white terns
Fairy Tern Sternula nereis
Damara Tern Sternula balaenarum
Little Tern Sternula albifrons
Saunders's Tern Sternula saundersi
Least Tern Sternula antillarum
Yellow-billed Tern Sternula superciliaris
Peruvian Tern Sternula lorata
Genus Phaetusa - Large-billed Tern
Large-billed Tern Phaetusa simplex
Genus Hydroprogne - Caspian Tern
Caspian Tern Hydroprogne caspia
Genus Gelochelidon - Gull-billed Tern
Gull-billed Tern Gelochelidon nilotica
Genus Larosterna - Inca Tern
Inca Tern Larosterna inca
Genus Chlidonias - marsh terns
Black Tern Chlidonias niger
White-winged Tern or White-winged Black Tern Chlidonias leucopterus
Whiskered Tern Chlidonias hybridus
Black-fronted Tern Chlidonias albostriatus (ex-Sterna albostriata)
Genus Thalasseus - crested terns
Lesser Crested Tern Thalasseus bengalensis
Royal Tern Thalasseus maximus
Greater Crested Tern or Swift Tern, Thalasseus bergii
Chinese Crested Tern Thalasseus bernsteini
Elegant Tern Thalasseus elegans
Sandwich Tern Thalasseus sandvicensis
Genus Sterna - large white terns
Forster's Tern Sterna forsteri
Trudeau's Tern Sterna trudeaui
Common Tern Sterna hirundo
Roseate Tern Sterna dougallii
White-fronted Tern Sterna striata
Black-naped Tern Sterna sumatrana
South American Tern Sterna hirundinacea
Antarctic Tern Sterna vittata
Kerguelen Tern Sterna virgata
Arctic Tern Sterna paradisaea
River Tern Sterna aurantia
Black-bellied Tern Sterna acuticauda
White-cheeked Tern Sterna repressa

Photos are presented for those species highlighted in red.