Three Monthly Instalments (2025)

Hi everyone,

I found this expression on a language teaching website (Lingoda):

Each plan will be paid in three monthly instalments

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Thanks,

Not at all - they're quite different things.

Three monthly instalments = January, February, March.
Tri-monthly instalments = January, April, July.

Keith Bradford said:

Tri-monthly instalments = January, April, July.

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Bimonthly is ambiguous and can mean every other month or twice a month. While our dictionary doesn't show that to be the case for "trimonthly," the word is rare and people in the real world don't look up words in the dictionary so let's add : or Jan 10, Jan 20, Jan 30.

Three monthly installments to me means that one installment is due every month for three months.

I add to Keith Bradford's comment about 'tri-monthly' that I would take 'tri-monthly' to mean every three months for an indefinite period of time. For instance: 'My parents give me an allowance on a tri-monthly basis' means that I get money every three months, but it doesn't indicate for how long my parents will keep giving me money.

'Three' describes the number of monthly installments.
'Tri-monthly' describes the frequency of the installments.

Thank you @Keith Bradford and @Myridon.

Keith Bradford said:

Tri-monthly instalments = January, April, July.

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Myridon said:

Jan 10, Jan 20, Jan 30

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Interesting and make sense at the same time!

But still I'm confused about the formation of the second part of the original phrase.
Does that mean it's possible to say "one monthly", "six monthly" and so on?

Sohayb said:

Does that mean it's possible to say "one monthly", "six monthly" and so on?

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Yes. You are paying three (or six) instalments, and you are paying them monthly.
One payment would probably not be called an instalment.

Roxxxannne said:

'Three' describes the number of monthly installments.

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Thank you @Roxxxannne. That clears up my confusion now.

Keith Bradford said:

Six monthly instalments means six instalments spaced out one month apart.
Six-monthly instalments (note the hyphen!) means any number of instalments spaced out six months apart.

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Perfect example. This sums it up.

Thank you very much!

USMeg said:

Yes. You are paying three (or six) instalments, and you are paying them monthly.
One payment would probably not be called an instalment.

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USMeg, do you (as a US English speaker) spell “installment” with one L? I would use two.

pob14 said:

USMeg, do you (as a US English speaker) spell “installment” with one L? I would use two.

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No. I was just conforming to the original version.

The base unit is a "monthly installment". It's one payment per month. The rest is just a description of how many of those there are.

A: You an pay for this refrigerator in monthly installments.
B: How many?
A: Our normal plan is six monthly installments. But we have a nine month plan, as well. That requires nine monthly installments.

Sohayb said:

But still I'm confused about the formation of the second part of the original phrase.
Does that mean it's possible to say "one monthly", "six monthly" and so on?

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If there is only one payment, it cannot be an "instalment", nor can it be associated with a period of time. However, if it is one of a number of monthly instalments, then this is fine ("I only have one monthly instalment left to pay").

It is also worth mentioning that "three-monthly instalments" is something very different from "three monthly instalments", even though they look and sound very similar. "Three-monthly instalments" are instalments that are paid every three months (and "three-monthly" sounds a far more likely term to me to use than "tri-monthly").