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.
In complex analysis, a rational function. is the ratio of two polynomials with complex coefficients, where Q is not the zero polynomial and P and Q have no common factor (this avoids f taking the indeterminate value 0/0).ote that the function itself is rational, even though the value of f (x) is irrational for all x. Every polynomial function is a rational function with. A function that cannot be written in this form, such as, is not a rational function.