You usually see these in a pronounciation key, over vowels; it means to pronounce the long vowel sound.
The letter "ā" with a line over it is a macron, which indicates a long vowel sound in linguistics. It is used in languages like Latin, Sanskrit, and Hawaiian to distinguish between short and long vowels in pronunciation.
10
It can mean that it is a vector.
No, it's an accent.
it means "without" from the Latin sans
That is sometimes used for the average.
a
With
In some of these letters, you will need a horizontal line over it. It means that for each line, you multiply it by 1,000. Since I can't do that for this, a "*" in front of a letter will represent a line over the letter. 8,657,846= **V**I**I*D*C*L*V*I*IDCCCXLVI.
It is a symbol for the word "with".
P with a bar over it means "after."p generally refers to 'post' or after, and can be seen with a line over it in written notes (as can the letter 'a' referring to 'ante' or before).
it mean everies
M with a line above it is the Roman numeral for a million.