<Estrone> is an <estrogen> whose <steroid> framework carries a <hydroxy group> at position 3 and a <ketone> <carbonyl group> at position 17. Its molecular formula is $\mathrm{C_{18}H_{22}O_2}$. The functional-group arrangement distinguishes it from other members of the <estrogen> family.<Estrone in ChEBI>[CHEBI:17263, Definition, Formula and estrogen role]{ref}

For a structural comparison, <estradiol> has a hydroxy group at position 17 in place of that ketone group. The distinction concerns the chemical form of the signal, whereas calling both compounds <estrogens> groups them by biological role. An assay reporting only one named compound cannot automatically stand for the whole class.<Estradiol in ChEBI>[CHEBI:23965, Definition and hydroxy-group positions]{ref}

A numerical example makes another distinction explicit. With average <molar mass> $270.372\,\mathrm{g\,mol^{-1}}$, $1\,\mathrm{nmol}$ of <estrone> corresponds to $270.372\,\mathrm{ng}$. The same number of moles of <estriol> has a greater mass because its molecular formula differs. Comparing equal masses and comparing equal molecular amounts are consequently different experimental choices, neither of which alone determines biological effect.<Estrone in ChEBI>[Formula and Average Mass]{ref}


 Estrone (source code)