A Linear expression is an algebraic expression that contains a variable to the power of one. 3 + y is an example.
A Coefficient is a rational number multiplied by a variable. A Rational Number is a number that can be written as the ratio, or fraction or intgers.
4 in the expresson 4x is an example of a coefficient.
Like Terms are terms whose variables and their exponent are the same. One example is 9y and -7y