The proper form depends on what you are abbreviating:
The form is a.m. or A.M. is an abbreviation for ante meridiem (before midday); used to designate the first twelve hours of a day (10 a.m.).
The form Am (no periods) is the chemical symbol for the chemical element americium.
The form AM (no periods) is an acronym for amplitude modulation, a term used in radio broadcasting (AM and FM).
Note: Today it is becoming more common to use AM as the abbreviation for time of day; I have taken to using that form myself. This is most likely due to the fact that so many people communicate by email or text, and students are often required to type assignments. It is just easier to type, and, for aging eyes, easier to read. But, whichever you use in your everyday life, you should know what is considered the "correct form".
proper
proper
A proper adjective is a descriptive word derived from a proper noun.Some examples are:Asia (proper noun) - Asian (proper adjective)Brazil (proper noun) - Brazilian (proper adjective)Canada (proper noun) - Canadian (proper adjective)Elizabeth I (proper noun) - Elizabethan (proper adjective)Sigmund Freud (proper noun) - Freudian (proper adjective)George Orwell (proper noun) - Orwellian (proper adjective)Proper nouns and proper adjectives are always capitalized.
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
what is trix
dearer , dearest
if you are talking about if it is a common noun or a proper noun, it is a proper noun.
proper noun
Pencil proper or common noun
proper noun
Exxon is a proper noun
As a noun, it's proper.