case 1 HYPOTHETICAL SITUATION
If I was rich, I would buy a new house. ✔
INFORMAL (OK, but grammatically wrong)
If I were rich, I would buy a new house. ✔
FORMAL (OK and grammatically correct)
case 2 FACT IN THE PAST
If I was stupid on the phone yesterday, I'm sorry! ✔
OK & grammatically correct
If I were stupid on the phone yesterday, I'm sorry!
NOT OK and grammatically wrong
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For more information, click here and here.
OBS.: The CASE 1 informal use is very common in songs. Here you have two examples:
- "If I was a rich girl..." GWEN STEFANi (click to watch)
- "If I was your vampire" MARILYN MANSON (click to watch)
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