I do not have printed (paper) dictionaries, so I use the on-line versions of the dictionaries.
sb in the Cambridge Dictionary:
sb = written abbreviation for somebody or someone
sth in the Cambridge Dictionary
sth = written abbreviation for something
Of course, several words / expressions can be abbreviated as sb or sth.
E.g.:
Sb = stibium (antimonium)
SB = Sound Blaster
other uses for sb
other uses of sth
I found all that with a simple Google search. All information was on the first page of results. I will not copy / paste all definitions from all dictionaries, as it is not the point.
Are these proper words?
Hell, no! :) They are abbreviations, of course (I hope).
I already asked a specific question here.
Can I use these words in my essays, for example?
As far as I know, academic papers, like any formal communication, should use the minimum amount of abbreviation. Of course, some "famous" abbreviations are allowed (etc., e.g., i.e., names of institutions...), but other than that, not really.
Can I use these words in my posts on Stack Exchange?
Stack Exchange is a (mostly) informal place of communication, so abbreviations are not forbidden. However, their use can be ambiguous, and they should either be avoided, or disambiguated (defined).
Example: one question was about PC. The first words that popped into my head when I saw that, were "Personal Computer". However, OP meant "Politically Correct".
Asking if they can be used on SE, particularly if you're asking about ELL should be done on the ELL meta page. – Catija – 2016-04-05T13:59:00.227
@Catija It's merely asking what types of environment this common English abbreviation can be used in. The fact that I've used ELL as an example environment, is just to make the question more immediate and pertinent to readers. That part could be asked on ELL meta too, I agree. – Araucaria - Not here any more. – 2016-04-05T14:07:31.040
1Abbreviations used in dictionaries are explained in the dictionary. Normally before the vocabulary part. – rogermue – 2016-04-05T16:39:56.877
@rogermue Yes, but some of the 'experts' answering questions here are unaware of these common abbreviations. And some of them are telling students off because they think they made them up because they are lazy. They are standard abbreviations within English language learning. – Araucaria - Not here any more. – 2016-04-05T21:35:23.603
Comments are not for extended discussion; this conversation has been moved to chat.
– ColleenV – 2019-03-27T14:12:37.750