A yabby is a small crayfish that is found in creeks, rivers and billabongs in Australia. They can be caught and eaten in much the same way as larger crayfish.
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.
Yoghurt is made from fermenting milk. Yoghurt is very sharp and tangy on its own. Modern yoghurt often has fruit and sugar added. Yoghurt is nice to eat on its own, with fruit or breakfast cereal, or frozen as a kind of icecream.