expression: An expression evaluates into (results in) a single value. type of expression: EXPRESSIONS THAT JUST ASSIGN A VALUE TO A VARIABLE EXPRESSIONS THAT USE TWO OR MORE VALUES TO RETURN A SINGLE VALUE example: var color = 'beige'. var area = 3 * 2 . operator: Expressions rely on things called operators; they allow programmers to create a single value from one or more values ASSIGNMENT OPERATORS. example: color = 'beige'. ARITHMETIC OPERATORS: example: area = 3 * 2 . WHAT IS A FUNCTION? Functions let you group a series of statements together to perform a speceific task . declaring function ? function sayhello(){ document.write("hello"); } calling function? you can excute all of the statement between curly braces with just one line of the code . sayhello(); declaring function that need information . give it parameter inside the function. function getarea( width,height){ return width*height; } calling : getarea(width,height); getting asingle value out of afunction some function return the information to the code that called them . function getarea( width,height) { var area= width* height; return area; } var one= getarea(3,5);