Idiom – R

Raining Cats and Dogs: A very loud and noisy rain storm
Example: Sometime you can say cats and dogs when it is raining heavily

Ring Fencing: to make sure that a sum of money is protected, especially project funds.
Example: The company established a ring fencing policy for improvements to the transport system.

Rise and Shine: someone to get out of bed and get ready for work
Example: We can say "rise and shine" to awaken someone. And "bright and shiny" is a couplet that we use for.

Rome was not Built in One Day: emphasize that you cannot expect to do important things in a short period of time
Example: You can't expect me to finish this project in the time allotted; Rome wasn't built in a day.

rule of thumb: A rough estimate
Example: A good rule of thumb is that a portion of rice is two handfuls.

Run out of Steam: to be completely out of energy or enthusiasm.
Example: The negotiation meeting is still carry on, they should be run out of steam already.