Assertion: acorn | /r/MadeOf | tannin
Facets:
Source sentences:
text: This is because they contain tannin, a bitter substance in oaks which is used to tan leather.
text: However, most acorns do contain enough tannin to make leaching this bitter substance out necessary.
text: Acorns also contain tannins, most obviously experienced by nibbling on a raw acorn of the black oak group (e.g., northern red oak, black oak, scarlet oak, pin oak).
text: Acorns contain tannins, which are toxic to some animals such as horses.
text: Acorns contain tannins, bitter compounds that not only taste bad but can upset tummies.