Definition of lumbar puncture. : puncture of the subarachnoid space in the lumbar region of the spinal cord to withdraw cerebrospinal fluid or inject anesthetic drugs.
Rational Numbers A rational number is a number that can be written as a ratio. That means it can be written as a fraction, in which both the numerator (the number on top) and the denominator (the number on the bottom) are whole numbers. The number 8 is a rational number because it can be written as the fraction 8/1.
Definition of a Rational Function. A rational function is a function that is a fraction and has the property that both its numerator and denominator are polynomials. In other words, R(x) is a rational function if R(x) = p(x) / q(x) where p(x) and q(x) are both polynomials.