Your definition of itch is correct. Itch is a sensation not an object therefore you don't talk about its size but rather its severity ( how intense the itch is) You could say eg. My head is so itchy. eg. My arm in plaster is extremely itchy. You may also want to say how much of your body is experiencing the itch. Eg. This scratchy jumper makes my whole back itch. Eg. I am itchy all over after standing on that ant hill. Sometimes you will hear people say I have I have a large itch. We all understand and you probably won't be corrected but its not technically correct. Also you may hear people say eg. Can you itch my back for me. This is wrong. You should always scratch an itch. Itch is not a verb. With reference to jumbo the above answers are correct. You may also hear it used in reference to large take away food sizes. Eg. A jumbo fries or a jumbo soda. In this case it would be a larger size than 'large'

It does, but it's not something you would use in every day talking. You wouldn't for example say, "I have a jumbo pimple on my chin!" meaning you have a very large pimple, etc. It's only really used for two things - when talking about elephants, and to be honest, I dont know why. You still wouldn't even use it when talking about elephants, it'd be more natural to say, "Man...that elephant is huge!" But anything an elephant HAS - say an itch...or particularly large ears...you could say it's jumbo then - referring to the elephant. The other use is a type of jet....a jumbo jet. And that's about it!

Yes, that's right

"Jumbo" is actually a reference to a circus elephant. Not just any elephant, one particular circus elephant. "Jumbo" was the name of a very large elephant, exhibited by P. T. Barnum in the late 1800s. He was an unusually large elephant and very famous. For a long time, his stuffed hide was kept at Tufts University in Medford, Massachusetts, but it was destroyed in a fire. In the United States, the three largest egg sizes are called "large," "very large," and "Jumbo" and that pattern is followed elsewhere. If something comes in a series of sizes, "Jumbo" can mean the larget size.