You usually see these in a pronounciation key, over vowels; it means to pronounce the long vowel sound.
10
It can mean that it is a vector.
it means "without" from the Latin sans
That is sometimes used for the average.
A line over the letter o, called a macron, typically indicates a longer pronunciation of the vowel sound in languages such as Latin or Hawaiian. It does not specifically mean "without" in all cases, but rather serves to differentiate between different vowel sounds.
In linguistics or phonetics, a line over a letter signifies that the sound represented by that letter is pronounced with a higher pitch or tone.
a
With
It is a symbol for the word "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.
the double dot is an umlaut, and i believe the line is called macron u
it mean everies