Help with English grammar

[Misandei]

Admittedly, too much time on MN has meant i’ve been reading the whole spectrum of grammar. I now do not know what is correct (or is it which is correct? See my dilemma?) or what’s wrong anymore. For instance I seem to read a lots of posts that use ‘what’, when I think it should be ‘which’, but perhaps I’m the one that’s wrong.

Example:

Poster - ‘What country are you from/in?’
Me - isn’t it ‘which?’

What universities have you applied to?
Isn’t it which?

What subjects are you doing for GCSE?
Isn’t it which?

I’ve also read so many posts where effect/affect have been mixed up I’m starting to second guess myself when using ‘affect’, I know most of them mean affect when they say effect but overtime it starts to look right.

I’m the one that’s wrong aren’t ?

What and which are generally fairly interchangeable. We always teach though, that what is preferred when the answer range is limitless. "What's your favourite colour?" Which is used when the answer range is more limited. "Which do you prefer, this one or that one?"

That said, using what instead of which wouldn't be wrong.

Sorry, clicked too soon- wouldn't be wrong in the majority of cases.

That’a a great way to remember which one to use. Thanks.

Affect is a verb and effect is a noun.

Except in the case of 'to effect a change' or similar, jeanne!

Yep. Affect is always a verb and means 'to have an effect on...' Effect is almost always a noun, except when it's used to mean 'to bring about' - e.g. 'effect a change', as mentioned above.

A good way of really seeing the potential difference between 'what' and 'which' is to use them in a question without nouns after them.

"What do you want?" (Could be anything)
"Which do you want?" (Implies choice between a given set of things)

But you can pretty much use them interchangeably with nouns as long as the context is clear.

Affect can be a noun, too... It's more a niche word meaning the manifestation of a feeling or emotion. You might hear people describing someone with, say, autism as having a unusual "affect" meaning their facial expressions aren't quite natural.

Good point, I'd forgotten about that usage. As you say, pretty niche.