An element that is not an actinide among typical choices would be one that does not belong to the actinide series, which includes the 15 elements from actinium (Ac, atomic number 89) to lawrencium (Lr, atomic number 103). Common examples of elements not in the actinide series compared in multiple sources are lanthanides such as terbium (Tb) or lanthanum (La), which are in the 4f series and are not actinides. In summary, elements like terbium (Tb) or lanthanum (La) are not actinides, while uranium (U), thorium (Th), and plutonium (Pu) are actinides.