Does the word English word 'typhoon' come from the Cantonese for 'big wind'? According to Webster's On-Line dictionary, typhoon comes from the earlier English word touffan, which ultimately comes from the Greek typhon meaning 'whirlwind'. Typhon is related to another Greek word typhein meaning 'to smoke', via the Arabic tufan for 'hurricane'. However, the modern-day English typhoon is also certainly thought to be influenced by the Cantonese taai fung. Typhoon first became part of the English language in the 16th century. Why do aircraft sometimes leave trails in the sky? ANNA WONG LAI-MAN Belilios Public School The white lines aircraft sometimes leave behind are condensation trails (contrails) from the engine's exhaust. A similar principle is at work when you breathe out and can see your breath on a cold day or when the air-conditioning is turned up too high. Contrails usually form at high al titudes of above eight kilometres when the air temperature is less than 40 degrees Celsius below zero. They do not usually form in dry air. In moist air, contrails can persist for a long time from a few minutes to more than a day depending on the conditions. What is a limerick? A limerick is a short, five-line verse that usually has a funny ending. The last word of the first, second and fifth lines should rhyme with each other. These lines should contain eight or nine beats or syllables. The third and fourth lines are shorter and should rhyme with each other too. These line should have four, five or six beats. Variations on the form date back to the 14th century. Even Shakespeare used it in his plays Othello and King Lear. Here is an example: A limerick should brighten your day Be witty, perceptive and gay. A neat little verse Will do nothing worse Than banish your bad blues away! For more fun with limericks, visit the Web site at http://teenwriting.about.com/teens and do a search for 'limericks'. Where is our funny bone and why is it called this? The funny bone is not really a bone, but a spot on the elbow where a nerve passes over the long bone in the upper arm. Sometimes when you bump your elbow by accident, it seems particularly sensitive or painful in that spot. People say: 'Ouch! I've hurt my funny bone!' Maybe this sensitive spot on the elbow became known as the funny bone because the bone in the upper arm is called the humerus, which sounds like the word 'humorous'.