Physics Class 9 Chapter 1 - Quantities and Measurement

What is the knowledge called that is gained through observations and experimentations? When you can measure what you are speaking about and express it in numbers, you know something about it. Who said this? When you cannot measure what you are speaking about or you cannot express it in numbers, your knowledge is of............................? From which language, the word science is derived?Which is the branch of physics that deals with the production, properties and applications of sound waves?