If by "am" you are referring to time, below is an example of Associated Press style:
10:30 a.m.
before a punctuation.
It's not a specific punctuation mark. It refers to using full (all) punctuation marks where necessary.
a close punctuation means a punctuation at the end of each sentence
A colon.
punctuation
before a punctuation.
It's not a specific punctuation mark. It refers to using full (all) punctuation marks where necessary.
a close punctuation means a punctuation at the end of each sentence
A colon.
None, open punctuation means there is no punctuation after the salutation or the complimentary close.
Grammar Diction Tone Punctuation
Words are not made out of punctuation.
No. A comma is a punctuation mark.
punctuation
an apostrophe is a punctuation mark.
There was no punctuation until the fifteenth century.
it is sometimes indicated by a punctuation mark