Good morning, class. Today's topic is "Idioms and Their Origins". An idiom is a phrase or expression with 1. The meaning of an idiom often cannot be understood from the meaning of 2in it. In our language, idioms are an important part and they often make our language 3. So in today's lecture, let's look at the origins of some English idioms. The first 4on our list is "Raining cats and dogs". This is an interesting phrase. It is 5the well-known antipathy between dogs and cats, which is 6in the phrase "fight like cat and dog". However, there are 7about the origin of the well-known expression, "Raining cats and dogs". One theory is that 8, the roofs on houses were made of hay. You've probably heard of 9, well that's all they were. Thick straw, piled high, with 10. Those thatch roofs were the only place for the little animals to 11. So all the pets in the house; dogs, cats and 12, even mice, rats, bugs, all lived in the roof. When it rained 13so sometimes the animals would slip and 14. Thus the saying, "it's raining cats and dogs. " Another explanation is that heavy rain would wash dead animals 15. In the 18th century, streets in England were rather filthy and heavy rain would occasionally 16dead animals and other debris. The animals didn't fall from the sky, but the sight of dead cats and dogs 17in storms could well have caused the coining of this colourful phrase. The most popular one comes from 18in which cats were a symbol for rain and dogs 19. Thus, "it's cats and dogs out there" is often used to describe 20with strong winds.