“Mourning”, “whining” and “wailing”

Question

I cannot differentiate the listed words below:

• Wail
  to make a long, high cry, usually because of pain or sadness, or to make a sound like this
  

• Mourn
  To feel or express deep sadness, esp. because of someone’s death
  

• Whine
  If you whine, especially as a child, you complain or express disappointment or unhappiness repeatedly
  

Please consider that, in many dictionaries, they have not been dedicated for a specific purpose while they emphasize by the adverbs "usually" and "specifically" in their definitions; hence, I don't know whether using each one in a particular case would be natural or not!

For instance, I don't know which choice would be more idiomatic and natural in each case below:

(First scenario) (informal case)
A: Why are you ____________?
B: Oh, you don't know how much my leg hurts.

(Second scenario)
A: Did you know that Ana's father passed away last night.
B: Seriously!!! What a catastrophe! I'm really worried about her! Have you heard of her since morning? Is she OK?
A: She is not OK at all!! Keeps sitting at home crying and ____________

(Third scenario)
- Last night, I couldn't sleep whatsoever! A cat was lying down on the wall ____________ just behind my sleeping room's window.

Answer 1

Wailing is crying loud and long. (Or, by metaphor, some similar sound.) It's a little archaic; normally you say crying instead.

Mourning = grieving: being upset because someone died. (Or, by metaphor, some other tragedy.) It's an emotion, not a sound, although it probably involves crying a lot. It probably lasts for months or years.

Whining can be a sound, in which case it's high-pitched and thin and usually not loud. A noise from insects or machinery may be described as a whine. But when it's used for a person, it's insulting and dismissive: someone who's whining is a child, and their complaint is not justified, and they're only pretending to be upset. You'd never describe someone who's mourning as "whining".

In your first example, none of these words is likely. Whining would be insulting: "Why are you complaining for no good reason?" Wailing sounds archaic here, and mourning doesn't make sense. "Why are you crying?" is more likely, but a native speaker would probably say "What's wrong?".

In your second example, Ana is mourning, but the last sentence is about what she's doing, not how she's feeling. Also, it's introduced with "keeps ___ing", which implies a repeated action — and mourning is a continuing state, not repeated. So you probably want wailing. (It overlaps with crying, but that's OK.)

In your third example, the concept is crying loudly, so wailing is the right word.