something
pron.a thing that you do not name specifically. You use it when you do not know exactly what the thing is or when the name is not important.
pron.an unspecified or unknown thing, amount, or event. Functions as an indefinite pronoun and typically takes a singular verb.
“I have something in my eye.”
“She felt something cold touch her shoulder while she was walking through the dark hallway.”
“The researchers noticed something unusual in the data, which prompted them to restart the entire experiment from the beginning to ensure accuracy.”
Always treated as singular; any following adjectives must be placed after the word (e.g., 'something blue' rather than 'blue something').
As a pronoun, it does not take an article like 'a' or 'the'.
Usage something else · something like · something different
From Middle English somþyng, some-thing, som thing, sum thinge, sum þinge, from Old English sum þing (literally “some thing”), equivalent to some + thing. Compare Old English āwiht (“something”, literally “some thing, any thing”), Swedish någonting (“something”, literally “some thing, any thing”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.