What do I mean by this? There are a great many people who speak English with glaring grammar mistakes or who use non-standard words. While some words or grammar mistakes are acceptable in some regions of the United States, they are not necessarily standard American English and should not be used in everyday conversational speech. Let's take a look at one word in particular that you will want to avoid using like the plague!
The word "aint" has been around for a long time, and originally started as a contraction for "am not", "are not", "is not", "has not", "have not", as well as "does not", "do "not" and "did not. You may hear it in informal speech, especially in certain regions of the United States. It carries a negative association with it and is often associated with individuals from a low socio-economic or educational background.
Is "aint" ever acceptable to use? The simple answer is "yes", but only in specific instances. There are times when using the word "ain't" is acceptable, but only as an expression that has become a famous quote, either from a movie or reported incident.
Probably the most famous use of "ain't" comes from an incident that was reported in the newspapers in 1920 when professional baseball player Shoeless Joe Jackson was leaving the courtroom after apparently been accused of taking a bribe to lose the 1919 World Series. On his way out of the courtroom it is reported that someone shouted to him, "Say it ain't so, Joe." There is a lot of controversy as to whether or not this statement was actually said, however it became well-known and has been used by many ever since.
The bottom line is that you should be careful with the words you choose to use. Don't repeat a word or expression that you hear just because you hear someone say it. Check it out to make sure that it is standard American English and that it is appropriate to use.