Scientific name: genus: dioscorea
A yam is the tuber of a vine, found in many countries around the world. Yam tubers can grow very big - up to 70kg. Yams have a rough skin that is hard to peel, but much softer flesh inside. Many people call sweet potatoes yams or sweet yams, but they are actually different vegetables. Some variety of yam can be eaten raw, but most need to be cooked. Yams can be fried, boiled, pounded down and made into a dough. They can also be dried and powdered and used to make something similar to instant mashed potato.
Yeast is a very tiny fungal organism. Some species of yeast are used in baking and brewing. Yeast can make bread rise and become light and fluffy, and it can be used to make some wines and beers. Yeast extract is used to make some very strongly flavoured spreads like Vegemite.
Scientific name: taxus baccata
The yew tree is a kind of conifer originally from parts of Europe, Africa, Iran and Asia. It is a small to medium, slow-growing tree, reaching around 10 to 20 metres high. The leaves and seeds of the tree are very bitter and poisonous. The yew's pine cones are unusual, being more like a berry with a single seed. The berries are eaten by some kinds of birds.