# Crisis of Notation, italic or roman subscripts?

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1. Apr 5, 2015

### Ashiataka

From the wikipedia article Physical Quantity
I'm having trouble deciphering the difference here between when roman or italic is appropriate.

Any further guidance?

Thank you.

2. Apr 5, 2015

### Enigman

My understanding is -
The quantity is always in italics.
Name reference - subscript refers to the concept or entity (usually with an abbr.); written upright.
Quantity reference - subscript refers to under what condition measurement was taken (with a symbol for the quantity taken as constant); written in italics.

Basically, accepted symbols are in italics; abbreviations are not.

3. Apr 5, 2015

### zoobyshoe

Notice, Ashiataka, that the choice is between upright or italic, not Roman or italic. Roman seems to be the conventional font, and it may either remain upright or be italicized.

4. Apr 5, 2015

### Staff: Mentor

From Wikipedia:

5. Apr 5, 2015

### Staff: Mentor

I concur with Enigman. Note that Physical Review has a different rule: all single-letter subscripts must be italic, even if they don't refer to a quantity. For example, the initial time could be noted $t_\mathrm{i}$, except in Physical Review where it must be $t_i$.

6. Apr 5, 2015

### zoobyshoe

I stand corrected. I thought Roman was a font that could be left upright, italicized, bolded, or underlined like any font.

7. Apr 6, 2015

### BobG

Yes, Roman, like any text, can be italicized on a computer. That's not the same as an Italic font, which can similarly be modified into an upright Italic font (one of the options when you need to italicize something in the middle of a text that's already italicized).

With computers and tons of fonts, you can italicize anything with that meaning "slanted letters" for a lot of the fonts.

In the old days of typesetting, italics was its own font and still is, even if not as significant anymore in normal text. Who the heck wants to actually change fonts all the time when using slanted letters is simpler and almost as effective.

Back in the days I used a typewriter, I just plain hated italicized text in a paper. I had to insert two blocks of wood, just the write size, under the two right feet of the typewriter in order to get just the right slant for the italicized letters.

8. Apr 6, 2015

### zoobyshoe

I guess my sense of it came completely from internet usage, and I never ran across the history.
Oh, the right side! I never had any luck with this because I was always blocking up the left side! My reasoning was that friction should prevent the bottom of the letters from moving while the tops fell to the right.