You should set some rules
about your In- Un- De-... then you could complain when we have it wrong. At the moment it's just guessing and "my father and teacher told me it was like that"; which is not useful when your father or theacher didn't speak any English.
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 11:58, 2 replies, latest was 14 years ago)

unuseful!

(Set your faces to Stunned Bigly, Wed 14 Sep 2011, 11:59, Reply)

Disuseful, you mean.

( Monty Boyce, My cheese game is strong, Wed 14 Sep 2011, 12:03, Reply)

Imuseful, ain't it?

( Kroney, Wed 14 Sep 2011, 12:06, Reply)

Sorry, it's usually due to which language the root word came from.
There's no real rule to it other than that.
( Kroney, Wed 14 Sep 2011, 12:00, Reply)

Like in the rest of your language
You're missing rules every where. And an Academy of the Language to tell you what's acceptable and what isn't. Barbarians!
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 12:02, Reply)

It's a bastard, mongrel language, to be sure.
That's why I think it's important to follow the grammar and spelling we have got. Save making the whole mess any worse than it already is.
( Kroney, Wed 14 Sep 2011, 12:06, Reply)

She's just being lazy
If she could bother her arse to learn Latin, Ancient Greek, German, Norse, Old-English, etc. she wouldn't have any problems knowing which word or prefix to use.
( tangledupinblue hairy badge with moving eyes, Wed 14 Sep 2011, 12:08, Reply)

Even like that
I think you probably will find thousand of exceptions and I'd end up even more confused.
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 12:10, Reply)

Just remember: the exception proves the rule
Or something.
( tangledupinblue hairy badge with moving eyes, Wed 14 Sep 2011, 12:11, Reply)

Yes, I know.
I've learnt a lot about English watching QI. It seems that a lot of the rules you learn at school have more exceptions than not, which means they are not rules anymore. The "magic E" is the only one that I can remember that still applies.
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 12:13, Reply)

I love magic E's.

(Set your faces to Stunned Bigly, Wed 14 Sep 2011, 12:17, Reply)

They no longer teach "magic E" in primary schools.
It is all split-vowel digraphs now.
( tangledupinblue hairy badge with moving eyes, Wed 14 Sep 2011, 12:19, Reply)

I've been thinking about home schooling my kid for the first 5-6 years
but I'll have to pay someone to do the English, because otherwise he's going to learn nothing.
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 12:22, Reply)

I agree
But you don't have any grammar rules for those "negative words"; so I can't follow any. I have to guess. Usually I check, but I thought unpolite was right. I was wrong, clearly oxforddictionaries.com/noresults?dictionaryVersion=region-uk&isWritersAndEditors=true&noresults=true&page=1&pageSize=20&q=unpolite&searchUri=All&sort=alpha&type=dictionarysearch
(Aberracion Life's getting very complicated, but a lot of fun., Wed 14 Sep 2011, 12:12, Reply)