Here is a notice I saw in a shop near my house. So what is wrong with it? Sure, we can work out that fish in this shop is likely to be cheaper at the moment but, to a native English speaker, the image that springs to mind is of a fish out shopping and very pleased to find that they get a super good deal in this shop.
OK, time to get technical.
What exactly is the problem with this sign?
It’s all to do with preposition use. Here the shop owner has used ‘for’. This suggests that a fish will receive a special offer. In the same way, we might say:
‘I have a gift for you’
‘I’ll get a coffee for you’.
The preposition ‘on’ is used in many ways. In this sense, a special offer ‘on’ something, it indicates that the price of this item is lowered. You can remember that ‘on’ is used in this sense as price stickers are often stuck ‘on’ items. So, the sign should read:
Special Offer on Fish
The use of ‘the’ here is also not needed. This is a really common problem amongst people who use English as a second language. ‘The’ is a definite article and so is used to distinguish one particular item amongst many. If we wrote:
Special Offer on The Fish
We would be referring to a particular fish, rather than all the fish in the shop.
So here, we can just put ‘fish’ as we are referring to some fish, or all the fish in the shop.