Reminder = something( eg . a letter) that helps someone to remember something; prompting.

• She hasn’t paid me that money yet – I must send her a reminder.
• Granny sometimes needed the old reminder.
• He’ll forget to call the doctor, if I don’t remind him.
• His stomach growled a reminder that he hadn’t eaten breakfast.
• His reminder of her failure left a bitter taste to her mouth.

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Remainder = (1) the rest ,balance, what is left when a part is taken away.

• Fifty members are elected directly and the remainder by proportional representation.
• The remainder of the population is chiefly made up of the Bangla speaking people from west Bengal.

(2) ,(math) what is left when a smaller number is subtracted from a larger one.

• An example of a remainder is the number 5 in the equation , twelve minus seven. 12-7 =5.