Final answer:
Lyla is thinking of an irrational number, which is identified by its infinite, nonrepeating decimal expansion.
Step-by-step explanation:
Lyla is thinking of a number that is a positive number with infinitely many nonrepeating digits after the decimal point. Such numbers are described in mathematics as irrational numbers.
To clarify, whole numbers are the set of non-negative integers without fractions or decimals. Integers include all whole numbers and their negative counterparts, but still no fractions or decimals. Rational numbers are numbers that can be expressed as a fraction of two integers, and their decimal expansion either terminates or repeats.
An irrational number, on the other hand, cannot be written as a simple fraction. Its decimal expansion is infinite and without any repeating pattern. Examples of irrational numbers include π (pi), √2 (the square root of 2), and 'e' (the base of natural logarithms).