Real Dictionary

-something
combining form: -something is combined with numbers such as twenty and thirty to form adjectives which indicate an approximate amount, especially someone's age. For example, if you say that someone is thirty-something, you mean they are between thirty and forty years old
combining form in countable noun: People of a similar age range are sometimes referred to as, for example, twenty-somethings or thirty-somethings.

-something in American English
of, relating to, being, or for a person of an age one to nine years more than (a specified multiple of ten)

-something in British English
combining form in countable noun: a person whose age can be approximately expressed by a specified decade

something
pronoun: You use something to refer to a thing, situation, event, or idea, without saying exactly what it is.

something in American English
a thing that is not definitely known, understood, or identified; some undetermined thing
adverb: in some degree; to some extent; somewhat
noun: a person or thing of some value or consequence
pronoun: some thing; a certain undetermined or unspecified thing