A fraction is not in its lowest terms if:

A fraction is considered not to be in its lowest terms when there is a common factor between the numerator and the denominator. This means that both the numerator and the denominator can be divided by a number greater than one, which allows for the fraction to be simplified further. For example, the fraction 4/8 has a common factor of 4; it can be simplified to 1/2, which is its lowest terms.

When a fraction is expressed in its lowest terms, the numerator and the denominator do not share any factors other than one. Therefore, the presence of a common factor indicates that the fraction can still be reduced, confirming that it is not in its simplest form.

In contrast, if the numerator is greater than the denominator, it does not necessarily imply that the fraction is not in lowest terms; it might still be fully simplified. The ability of a fraction to convert into a decimal does not indicate its level of simplification and thus is irrelevant in determining if it's in lowest terms. Lastly, both parts being whole numbers is a standard attribute of fractions but does not pertain to whether it is in lowest terms.