what is the difference between these two sentences

You are rude
You are being rude.
Hello RK

1. 'Rude' as in 'ill-mannered', 'offensive':

(a) 'You are rude' = 'You are offensive'.

(b) 'You are being rude' = 'What you are saying is offensive'.

2. 'Rude' as in 'indecent':

(a) 'You are ***' = 'You are making jokes or comments of an
indecent nature, but I'm quite enjoying them'. [Best avoided by
non-native speakers, as context is all.]

(b) 'You are being rude': I'm not sure it's possible to say this in a
'rude = indecent' context without sounding slightly camp, so again,
it's probably best avoided.

Meanings 1(a) and 1(b) are (I think) the ones you need.

"You are being rude" can only be said while the person addressed is behaving badly.
"You are rude" can be said at any time after you have concluded that the person addressed is generally a rude person. This may be after a long while observing the behavior of that person, or it may be an immediate reaction.

Another way to look at it is "temporary and permanent" or "states and traits":
"You are being rude" tells how the person is behaving at the moment (current state; temporary)
"You are rude" tells how the person behaves characteristically (personal trait; permanent).

Emotion: geeked
Students: Are you brave enough to let our tutors analyse your pronunciation?
'You are rude' - Implies that the speaker is concious of or is deliberately causing offence and the term is used as a rebuke. I suppose it could also mean that the person in question is well known for his bad manners.

'You are being rude' - Is less harsh than above and would be more aptly used if you wish to gently chastise someone or warn them that they are being rude without knowing it.
 CalifJim's reply was promoted to an answer.
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