noun
1
BAD : She had bought the ring at a jewellery.
GOOD : She had bought the ring at a jeweller's.
BAD : I saw the same watch in a jewellery shop.
GOOD : I saw the same watch in a jeweller's.
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jewellery = rings, bracelets, necklaces, watches, etc: 'The stolen jewellery has never been recovered.'
jeweller's = a shop which sells and repairs jewellery: 'I took the watch to my local jeweller's but they said it couldn't be repaired.'
2
BAD : You should keep expensive jewelleries in a bank or safe.
GOOD : You should keep expensive jewellery in a bank or safe.
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Jewellery is an uncountable noun: 'The thieves took nothing but cash and jewellery.'