By Mary Morel
Reader’s question: Which is correct?
He is younger than me.
He is younger than I.
Answer: ‘I’ is more correct in formal English, but ‘me’ is acceptable in informal English and is increasingly used in formal English too.
‘I’ is more ‘correct’ because you’re comparing two subjects.
However, when I did some more more research, I discovered that the distinction also hinges on whether you regard ‘than’ as a conjunction or preposition.
If you see ‘than’ as a conjunction, then ‘He is younger than I’ is correct. The second construction, ‘He is younger than me’, is using ‘than’ as a preposition and this construction has been around since the C16.
Read Grammar Girl’s post on this topic.