Edwin Burton Uline has written:

'Studies in the herbarium' -- subject(s): Accessible book, Dioscoreaceae, Amaranthaceae

The Latin name of Mexican yam is Dioscorea mexicana.

Yellow yam is a starchy tuberous vegetable grown on a vine. Variations are common all over the world, but especially in west Africa. Contrary to popular myth it is NOT the same as a sweet potato.

Yams are monocots. Sweet potatoes are dicots.

Most things people find in grocery stores in the US labeled "yams" are in fact a variety of sweet potato. These are members of the Solanaceae family (along with tomatoes, peppers, eggplants and deadly knight shade). They are dicots.

True yams are members of the family Dioscoreaceae. They are monocots.

There are seven different species of yam which are cultivated in Africa, Asia, Latin America, the Caribbean, and Oceania. They are all members of the Dioscoreaceae family. Keep in mind that this is the true yam, which does NOT include the sweet potato-type vegetable produced in the US for North American consumption. Those are a completely different plant.