Probably short for "something". See definition #1 here:

http://www.urbandictionary.com/define.php?term=sth

its a terrible shorthand for "something". I always read it as "sith".

I am from India and so I grew up on British English and have stuck to that. I was gifted a Oxford Pocket Dictionary when I was a kid, by an uncle. I practically learned my English with that dictionary, had it till recently when I passed it down to my niece(who is in 5th grade as of now).

Now, you'll have to trust me on these two statements:

1. I did learn "sth 'can' be used for something" from that old good little dictionary[1] and did not pick it from the Internet or SMS and it's a valid use. (Though, I see it also means South in US Eng)

2. That is probably the best dictionary I've come across, even better than OALD, I had them both and hardly ever used the latter (:-) ).

[1]http://dictionary.cambridge.org/dictionary/british/sth?q=sth - not Oxford link but just as good.

Same here in China. I grew up learning English using mostly British textbooks and sth is introduced to us quite early, pretty much like xyz in algebra. I'm actually quite surprised to find out it's perhaps not that common in the US.

In my experience you'd be hard pressed to find 'sth' used in the US (same for sb), most people would type it out to avoid ambiguity with 'south' and other words. In SMS and other short formats, phonetic spellings like 'sumthin' are more common.

I've only ever seen South abbreviated as S, never as sth.

I grew up in England learning English. sth is not very common here either.

Thanks for the explanation. I grew up in the USA, and covered a fair bit of British literature in school, but I've never encountered this usage before.

It's "something".