While reading Swan's Practical English Usage, I came across this sentence
I don't do much sport now, but I did play football when I was younger.
Why comparative younger? Simply young could have worked there, couldn't it? Or, does it mean that 'younger' means the speaker just left playing sport last year? As it reflects younger as the phase of life earlier than the present year (of his age).
For instance, if the speaker is 45…
I don't do much sport now, but I did play football when I was younger (than this age) -> Up till 44 he played OVER
I don't do much sport now, but I did play football when I was young -> When he was young, say in 20s-30s or whatever.
Best Answer
Young is the time of life before adulthood, synonymous with youth.
When I was young. = When I was a youth. Before my adulthood. This wouldn't make much sense for a 10 year old to say, but they may. Also, someone that is 100 may use young to refer to their twenties, even though that is adulthood.
Younger is comparative with the current age.
When I was younger. = Ages prior to my current age. This obviously depends on context. If you are 100 then younger could be 90, however in the context of playing football that is not as likely.