The group of spices I'm calling the cardamoms are all the seed pods and seeds of various ginger (Zingiberaceae) species. Currently they come from 4 Genera- Aframomum, Alpinia, Amomum, and Elettaria. Together these Genera have over 20 spices that are variously called (something)cardamom in English.
grains of paradise, Cameroon cardamom, Ethiopian cardamom, malinga pepper
Alpinia is a genus that has the spices Galangal and Lesser Galangal. Those spices are made from the rhizomes, but there is also at least one example of a spice made from seed pods. Elegantly called Violet Cardamom, Alpinia katsumadai is currently the only cardamom type spice from the genus Alpinia.
Of all of the cardamoms the genus Amomum offers the most interesting set of spices. This are more then 7 species that offer unusual spices, including Chinese Black Cardamom, Indian Black cardamom, and White Cardamom. There are also several members that lack proper English names, I can pull from the Chinese characters used to derive some simple names such as long cardamom, ridged cardamom, mulberry cardamom, and scaly cardamom
Amomum costatum- Chinese Black Cardamom, also known as Amomum tsao-ko
Amomum tsao-ko- Chinese Black Cardamom, also known as Amomum costatum
Amomum compactum- White Cardamom, alternate name to Amomum kravanh
Amomum kravanh- white cardamom also called Amomum compactum
Amomum testaceum- may be another name for A. kravanh
Amomum villosum-
Amomum longiligulare-
Amomum villosum var. xanthioides- A species used as a spice and as medicine from Northern Vietnam 1)
We return to a genera with one primary species, and this one is the most well known of the whole group and that is Green Cardamom.