Why does "pound" abbreviates "lbs."

And the bonus question:
Is there any rule on why and when to use the ampersand "&" instead of 'and'?
I feel it's a fashion that stayed in the English language, because we don't really use it in Latin Languages.

Thanks in advance

lb stands for libra = pound in latin

& isn't really used very often in English nowadays - it looks clunky. you can see it if you read old texts though. the only place you really see it these days is on signs

From elsewhere on the web, since I'm too knackered to ponder it myself: "The origin is in the Latin word libra, which could mean both balance scales (hence the symbol for the astrological sign Libra, which was named after a constellation that was thought to resemble scales) and also a pound weight, for which the full expression was libra pondo, the second word being the origin of our pound." We stay use pounds as a measure of weight in America (as opposed to kilograms), so its use is relevant here. Less so in metric lands, obviously!

The rule about "and" and "&" is pretty vague. Most educated people avoid "&" in anything involving formal writing, although it was a fashion to use "&" in books and whatnot during the (American) Colonial era and at other points - but generally only when listing objects - as in "oranges & lemons & apples . . ." This leads me to believe that the ampersand originally had the function somewhere between the word "and" and a present-day comma in listing items. (Today we would normally write out a list of objects as "oranges and lemons and apples . . ." or use a comma to separate them as in "orange, lemons and apples . . .") But I'm just guessing - its function could have been something as simple as a way of making life easier for a typesetter. It's used commonly as an abbreviation in e-mail and memoranda with no sense of a "rule" being involved particularly - not that writing out "and" takes much effort!

IMHO, aliled has hit the nail on the head.

I think it's likely that the ampersand was originally used, as were many abbreviations, at a time when writing was done exclusively by hand and writing materials were expensive. Old manuscripts are filled with instances of omitted letters represented by apostrophes or other marks as well as more or less standardized abbreviations, even for proper names.

As to rules, the ampersand is rarely used in narrative text and never in formal writing. It is mostly reserved for signs, titles and lists of names (John & Mary Smith).

Tae be fair: methinks chijimi hit the nail on the head; aliled hammered it home.

Tae be further fair: "the only place you really see it these days is on signs". Yes - all over my local market and, indeed, in my writings, albeit elsewhere!

The ampersand is a abbreviation of "et cetera", which can be roughly translated to mean "and so forth ...." or " and so on...".
Again it stems from Latin usage, and is an old scribes mark for "etc."
It has been all to often mis-used, as a stand-in for "and".
Today it typically appears in trademarked names, as in "Proctor & Gamble".

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<hr>The ampersand is a abbreviation of "et cetera", which can be roughly translated to mean "and so forth ...." or " and so on...".<hr></blockquote>
No: "&c" is used for "et cetera"; & is an abbreviation of Latin "et", which means "and".

#7 - I think it's merely "et" (meaning "and") rather than "et cetera". You can find examples in old texts of "et cetera" abbreviated "&c." In some fonts the ampersand actually looks like the word "Et".

#9 is right. It starts out as a curvilinear E with a cross on the extended base. Crossing a bit of the letter was common to indicate an abbreviation in medieval and modern Latin. per was abbreviated as p with a crossed tail. Recipe ("Take up" or "gather together", the first word in a formula) was abbreviated R with a cross on the extended right leg, still a symbol used for pharmaceutical prescriptions.

On second thought, I think I learned here that it's not so much an abbreviation as a digraph, e and t written as one letter, like a + e -> æ.

#11,
I believe the appropriate term is 'ligature' (as in 'linking') rather than 'digraph'.

I can only speak for U.S. usage, but in my country, the "&" symbol is almost universally used when joining initials. For example, it's AT&T, not AT and T. In Philadelphia, the Department of Licenses and Inspections is L&I, not L and I.

The ampersand is also used in some business names, particularly those consisting of two or more surnames: Smith & Wesson, Johnson & Johnson.