For one thing it [typically] has a top-right stub.

hhp

You’re joking, right?

David, any question can be considered on various levels. This particular question does make sense on a certain level. Think for example of a low-res bitmap font, or an abstract futuristic design. In some cases I can see the monocular /g and the /9 being distinguished only by the former having a sharp top-right and the latter a soft one.

BTW, I handwrite my /9 with a top-right stub, and many people misread it as a "g".

hhp

@Hrant: If we relied on your definition of lower case g and the difference between it and the number 9 the world would stop turning. Wonderful Hrant, I don't know what I would have done if I had remained on those hot coals burning my pretty flesh."In some cases I can see the monocular /g and the /9 being distinguished only by the former having a sharp top-right and the latter a soft one." If that's all you can offer as an example it makes me wonder how small your brain is. What about the curving tail of a 9 contrasted with the straight back stem of a single story g? A competent type designer would have mentioned that. Low res bitmap fonts and futurist abstract fonts don't count for diddley poo. How often do they get used?

@Ryan: the number 9 is typically drawn with a huge great oculus or bowl, whereas lower case g is drawn with a smaller bowl and larger stem and tail in proportion. The biggest giveaway is context. Who puts a number nine in the middle of words in place of lower case g's? Only a moron would do that. The 2 glyphs are distinguished by context, okay honey? The letters to the left and the right define them as g's. Let's look at an example. "Aggravated assault" Lookee yar, Ryan Maelhorn wonders if the 2 glyphs after "A" are g's or number 9's. Ryan, when you type the word "aggravated", do you put nines in there instead of g's? You know the answers to all of these questions already, and you are only here asking typophile to get attention. If you're going to be a typographer I would expect you to see these basic truths as self-evident, with no need to ask what the difference is. But you allow your silly ego to get in the way of common sense. Happy happy, joy joy.

Actually, the most common difference is that in lining figures, /9/ is placed higher than /g/. And isn't old-style figures really a source of confusion between /9/ and single-story /g/?

Sense, above, suggests the potential for confusion, while showing characteristic differences.
(Dax pushes further in that direction.)
Eunoia Rounded, below, might have achieved equivalence, if it had been given oldstyle figures.

As an aside, I once took some liberty with a Latin /g in making it look a bit Cyrillic, and it started drifting towards a /9! Here it is (next to the Cyrillic "be"):

And as an aside on my aside:
http://www.flickr.com/photos/48413419@N00/266618453/in/set-7215762712773...

hhp

Astonished at some of the invective shown on here.

Who puts a number nine in the middle of words in place of lower case g's? Only a moron would do that. The 2 glyphs are distinguished by context, okay honey?

Anyone remember that 1995 film with Kevin Spacey, Brad Pitt and Morgan Freeman in it? I think it was called Se7en. Everyone seemed to "get it" at the time despite the juxtaposition of letters and numbers and, although I have a bit of a jaded view about marketing types, I am fairly sure they weren't all morons.

Please don't feed the troll.

The lowercase single story g has a hard vertical feel to the right side of the first stroke, and it's arc doesn't start until well below the bowl(s) of the letter. Whereas the figure 9 has a smaller counter, and the arc reaches up into the bowl(s)

??????

Ryan, are you offering that explanation as an example of too strict a definition, or what? I don't get your questionmark sextet.

To me what characters are is both more complex and simpler than that sort of thing.

hhp

the strictest and most universal definition. The lowest common denominator.

Does not compute.

Here's how I roll: a (mono) /g is a blob with something coming down the right half, shifting leftward (so it's not a /q). A /9 is a blob with something coming down, preferably not left of center (even center is fine). If you're going to mix alphabetics and numerics (like in a username, password or TinyURL, so not crazy) then you want a singularity on the blob of the /g, preferably towards the top-right. BTW, [mis]alignment does not qualitatively disambiguate.

Alfred Kallir, where are you when we need you?

hhp

excellent answer

A g is a circle with a fishhook attached, a nine is a loop with a tail at the bottom.

Interestingly, for me when I print, my 9 and q are indistinguishable:

29 go que

Context and baseline are the only way to tell them apart... I never noticed.

I've know for a long time my 2 and z are exactly the same, so I cross the z (and 7, must cross my 7).

2 z 7

It's not type, but it affects my thinking and design process.

Mcs

I'd never noticed this happening before, but earlier today I submitted a text image of a sans serif typeface to WhatTheFont and it interpreted the 'g' as a '9'. It didn't do too well on other characters, either.

.

I think the differences so far mentioned here are valid ones, even if they don't apply to all typefaces:

- the right side of the 9 is usually a single curve, while that of the g is usually a straight line which is has curved parts at top and bottom;

- the straight line at the right of the g is attached to a circle, and so extends upwards past the point of contact, while the 9 is basically a single line with a spiral-like shape;

- the bottom of the 9 continues pointing downwards until the end, while that of the g forms a bowl that turns back up;

- the 9 stands on the baseline in the more common ranging numbers, while the g always has a descender.

- the bottom of the 9 continues pointing downwards until the end, while that of the g forms a bowl that turns back up;

Depending on style.