Not entirely. Payment by instalments (AmEng installments) is a way of buying something by making a series of small payments (usually weekly or monthly) to the seller. The size and number of instalments is agreed at the beginning, the item is handed over, and the buyer uses the item. Depending on the terms of the purchase, the item may legally belong to the buyer after the first instalment, or it may legally still belong to the seller until the last instalment is paid (hire purchase). The 'item' could be a loan - these can often be paid off by instalments. A monthly payment is any regular payment made every month. Examples of monthly payments which are not instalments: - Mortgage - I don't pay monthly to the seller, but to the bank. - Car lease purchase - I pay the seller regularly but I don't own the vehicle on making the final payment: there is a separate, optional 'buy out' payment after that. - Regular payment plans for dentistry or electricity - I pay for what I use, averaged over time; sometimes I have paid more than I have used, sometimes I have used more than I have paid. From time to time the payments change.

Yes except that an installment does not have to be monthly. It can be weekly, bi-monthly or monthly. Depending on the installment contract. :) In South Africa you can purchase property on an installment basis you would then have an annual installment.

Yes and no. You make a monthly payment(installment/equal amount every month) for your car (until it is paid for)and you make a monthly payment for your electricity or water but you don't generally make installments on utility bills unless you make special arrangements with the company, and usually under extenuating circumstances. So, only when you buy on credit, do you have to pay back in installments. But when referring to this installment you can call it a monthly payment. Again, we generally don't call our monthly bills installments.