Valid or invalid variable name?

sizeOfCircle

Valid variable name (uses camelcase)

circle size

Invalid variable name: Cannot include space

1count

Invalid variable name: Cannot start with a number

$cost

Invalid variable name: Must begin with a letter (usually lowercase)

count

Valid variable name

triangle-size

Valid variable name (dash is ok)

triangle_size

Valid variable name (underscore is ok)

homeAddress2

Valid variable name (uses camelcase and digits)