A month of Sundays.
A month of Sundays is a long period of time: I haven't seen her in a month of Sundays.
If things are A OK, they are absolutely fine.
A penny for your thoughts.
This idiom is used as a way of asking someone what they are thinking about.
A penny saved is a penny earned.
This means that we shouldn't spend or waste money, but try to save it.
A picture is worth a thousand words.
A picture can often get a message across much better than the best verbal description.
A poor man's something.
Something or someone that can be compared to something or someone else, but is not as good is a poor man's version; a writer who uses lots of puns but isn't very funny would be a poor man's Oscar Wilde.
A pretty penny
If something costs a pretty penny, it is very expensive.
A problem shared is a problem halved.
If you talk about your problems, it will make you feel better.
A rising tide lifts all boats.
This idiom, coined by John F Kennedy, describes the idea that when an economy is performing well, all people will benefit from it.
A rolling stone gathers no moss.
People say this to mean that that an ambitious person is more successful than a person not trying to achieve anything. Originally it meant the opposite and was critical of people trying to get ahead.
A slice off a cut loaf is never missed.
Used colloquially to describe having sexual intercourse with someone who is not a virgin, especially when they are in a relationship. The analogy refers to a loaf of bread; it is not readily apparent, once the end has been removed, exactly how many slices
A steal If something is a steal.
it costs much less than it is really worth.
A still tongue keeps a wise head.
Wise people don't talk much.
A textbook case.
A textbook case, it is a classic or common example of something.
A watched pot never boils.
Some things work out in their own time, so being impatient and constantly checking will just make things seem longer.
If something is A1, it is the very best or finest.
Abide by a decision.
If you abide by a decision, you accept it and comply with it, even though you might disagree with it.
Abject lesson (India)
An abject lesson serves as a warning to others. (In some varieties of English 'object lesson' is used.)
About as useful as a chocolate teapot.
Someone or something that is of no practical use is about as useful as a chocolate teapot.