Could you please explain the difference between those two words - "retiring" and "retirement"? To me they both indicate the time when you stop working but I can't quite pinpoint the difference in usage. for example "What is the legal age of a. retirement/b. retiring in your country?" Which do you think is more correct and why? I have frequently heard this phrase "retirement age" but i still doubt whether it's correct here. Thanks in advance.
"Retiring" as a verbal noun (a 'gerund') is only used in the sense of "the process of stopping work", whereas "retirement" is used more often of the resulting state.
So when you talking about the act
I'm thinking of retiring next year.
I'm thinking of retirement next year.
is possible, but to me means that you are thinking of the state of being retired, not of the process of retiring.
I'm going to enjoy my retirement.
You can't use "retiring" there.
Clearly this isn't the whole story, because it would imply that, in your example, we would say "the legal age of retiring". But, while this is possible, it is not natural. I think set phrases all use "retirement": "age of retirement"; "retirement party"; "retirement present".
As others have pointed out "retiring" is also a participle and an adjective.
is a verb meaning "going into the state of retirement
After 20 years, he will be retiring
He will retire in 20 years
after 20 years he will stop working
is a noun (or adjective) describing the the state of being retired
After 20 years, he will be going into retirement
When he retires, he will be moving to a retirement community
After 20 years, he will be retiring and start his retirement in a sunny location.