noun
BAD : He'd left all his tennis stuffs at home.
GOOD : He'd left all his tennis stuff at home.
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Stuff is an uncountable noun: 'He asked if he could bring his stuff over to my place.'
noun
BAD : He'd left all his tennis stuffs at home.
GOOD : He'd left all his tennis stuff at home.
◆◆◆
Stuff is an uncountable noun: 'He asked if he could bring his stuff over to my place.'
Longman Common Errors English vocabulary. Английский словарь распространенных ошибок Longman. 2012