Do impertinent and impudent have different meanings? What is the difference between impertinent and impudent?
They are synonyms with very close, essentially the same meaning:
Impertinent means: Exceeding the limits of propriety or good manners; improperly forward or bold. (The etymology is "not pertinent", "does not hold" from Latin.)
Impudent means the same thing: Offensively bold or disrespectful. (The etymology is "not pudent", "not ashamed" from Latin.)
These words are close synonyms of each other. The Oxford Dictionary Online defines impertinent as
Not showing proper respect; rude.
with synonyms rude, insolent, impolite, unmannerly, ill-mannered, bad-mannered, uncivil, discourteous, disrespectful
and impudent as
Not showing due respect for another person; impertinent.
with synonyms impertinent, insolent, cheeky, audacious, brazen, shameless, immodest, pert
The actual definitions are very similar and impertinent actually forms part of this definition of impudent. There are, however some subtle differences.
Firstly impudent has only one definition but impertinent has the secondary definition
Not pertinent to a particular matter; irrelevant.
This is a much less frequently used meaning but could confuse you if you are not aware of it.
Secondly there is a slight difference in the usage. While both words can describe an attitude of disrespect for a person impertinent can also describe an attitude of disrepect for an institution or other entity. For instance one of the many sample sentences for impertinent is
There's no choice but to speak ill of the dead and ask impertinent questions about the emperor's clothes.
Thirdly the lists of synonyms show a slight difference in style, the list for impertinence shows a bias towards seriousness and deliberate challenge but the list for impudence indicates a somewhat more light-hearted and more casual intent.
There is a very large overlap in the definition and usage of both words, but only when the disrespect is shown to a person.
When applied to person A's attitude to person B (for example that of a pupil to a teacher) they are virtually identical although impudent would be more likely to be used if there was an element of humour in the actions or words of A.
If, on the other hand, A was being disrespectful to an institution or organisation, particularly if there was a deliberate challenge to its authority, the correct word would impertinent as impudent is used specifically in relation to people. For instance questions relating to sexual abuse by priests might well have been called impertinent by the Church hierarchy in the early stages of the media investigation into it but would not have been called impudent as they were directed at the church as an institution.