The English language phrases To Remind Politely and Gentle Reminder are used quite frequently between adults who do not know each other. Here is how they are different, using British English examples.
A Gentle Reminder is a way to give information to people who should already know what is being said, but in a polite way, not assuming they have forgotten. For example, in a hotel, the manager might say:
"This is a gentle reminder that breakfast ends at 9am tomorrow because of the building works."
A colleague might say:
"Please give them a gentle reminder that checkout is at 1pm tomorrow."
To Remind Politely is a phrase that should only be used by the recipient of the information, because politeness is decided by the listener. The speaker can not demand their words are taken as being polite. The speaker should not say they are being polite, only that someone else is being polite.
The guests might be talking to friends about their hotel trip some days later, saying:
"The manager reminded us politely that breakfast hours were shorter that week."
In fact, you will often see notices saying something like "Polite Notice. Do not park here after 10pm as the gates are locked". In my opinion this is wrong, for the reason above, the writer can not demand something is taken as being polite.
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