WordNet sense 1 (a fat-soluble vitamin that is essential for normal reproduction; an important antioxidant that neutralizes free radicals in the body):

tocopherol, vitamin E

WordNet sense 2 (a radioactive transuranic element produced by bombarding plutonium with neutrons):

einsteinium, Es

WordNet sense 3 (the cardinal compass point that is at 90 degrees):

east, eastward, due east

WordNet sense 4 (the 5th letter of the Roman alphabet):

letter e