Reporting from US: "Falls ill" is very formal; "falls sick" doesn't work, in that it mixes a casual and a formal register.
This is really interesting how English is developing so many differences. Here in the UK, " to be sick" = vomitting; we usually say someone is ill, or becomes ill quickly, and the use of "get sick" just sounds, well, American. (Sorry guys!) What also interested me in these exchanges is the implications in using "readily" or "easily" - does it simply mean the son is ill often? Or is he a bit of a hypochondriac? Or maybe even a malingerer who is conveniently ill? As always, it's all in the context- which Duo doesn't give. It's quite fun to imagine, though .
Well, in the UK "to be sick" can mean to vomit, but it can also just mean to be ill, can't it. If I say "I was sick in bed last week", I probably don't mean that I actually vomited into the bed :)
Could someone please explain this sentence structure to me? If I was aked to translate this from english, I would have translated it as "Mon fils tombe malade facilement." Is that correct too?
What about "My son easily becomes ill"? It currently doesn't accept this translation, is the word "become" not used in this context?
Your sentence does have essentially the same meaning, Harrybear, but keep in mind that tomber = to fall.