What is a 'lump sum'?

[Pi]

Test No. incompl/advan-11 "Finance", question 4

When you retire, you should get a pension and a ......... sum from your employers.

(a) lump
(b) block
(c) pile
(d) heap

Test No. incompl/advan-11 "Finance", answer 4

When you retire, you should get a pension and a lump sum from your employers.

Correct answer: (a) lump

Your answer was: incorrect
When you retire, you should get a pension and a heap sum from your employers.
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What is the difference?

[Torsten]

A lump sum is a fixed expression, it means a total sum or an inclusive total.

A heap of is an informal expression for a lot of.

TOEIC listening, photographs: A dancing troupe

[Gheon]

Besides, lump sum payed only once (synonyms are one-time fee, one-off payment & immediate compensation)
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