What does f mean when refering to aperture f-stops?

I went to Google and found it mentioned as 3 different words - Focal, Fractional and Factual. 

So what does the 'F' mean in f/1.4?  

ƒ is not an absolute value but is symbolising a ratio in an
optical system, it refers to {focal length : entrance pupil}.

So the f means "Focal"?  

No Liem, it is just a symbol that represents a ratio in
an optical system. Just like Ω represents a resistance
in an electo-engineering system.

I think it refers to focal length, but it is a fraction of the focal length.

So it's not the actual focal length from the film/sensor to the end of the lens, it's a fraction of the focal length. For example, I think it means the size of an aperture of f8 is equivalent to 1/8 the focal length; an aperture of f16 is 1/16 the focal length, f2 is 1/2, etc.

G'day Liem

The wonders of a beaut forum such as this is that you can receive multiple correct answers from people

Both NS and Sharon have come up with the goods ... and now I shall offer you some more > just to "confuse" you some more!

Our photographic world revolves around mathematics - lens focal lengths are designated in millimetres, the exposure times in early days were given in whole seconds ... and as film emulsions became more sensitive to light, the times reduced to fractions of one second - ie: from 10 seconds to 1-sec to 1/2sec or 1/100s and so on.

At the same time early lens designs [simple lenses like a magnifying glass] had poor edge starpness, photographers discovered that if they inserted a donut shaped device into the lens, it did 2 things - a) it increased the edge sharpness, but at the same time it b) reduced the light entering the camera therefore increasing the exposure time needed

In order to try to make a constant alteration for shutter speed when different "donuts" were used, they came up with a simple formula whereby the hole in the donut was a fraction of the focal length of the lens. So for a 100mm lens, if the hole was 25mm in diameter it was "1/4". But this collided with the exposure time of "1/4 second" ~ so the industry inserted the symbol "f" into the aperture number to show exactly what it was referring to.

So now we have exposure data showing something like "1/250s @ f8" to designate exactly what exposure was used by the photographer in the creation of the image

Hope this helps
Phil from the great land Downunder
www.flickr.com/photos/ozzie_traveller/sets/