Grammar - Thought/ was, is

[lissatan]

Hi everyone. What’s the difference between “I thought she was a teacher” and “I thought she is a teacher” ?

 

[emsr2d2]

The difference is that a native speaker wouldn't use "is" in that sentence. Using "was" in that sentence means you think she's a teacher now (yes, I know it seems weird!)
If you want to refer to her past profession without a time marker, you'd say "I thought she used to be a teacher".
With a time marker, you could say "I thought she was a teacher in 2019/last year/once upon a time".

 

[probus]

Hello @lissatan and welcome to the forum. This phenomenon, the apparently illogical use of the past tense when referring to present circumstances, is called backshifting. If you search this forum for backshift or backshifting you'll find several helpful threads.

 

[jutfrank]

Using "was" in that sentence means you think she's a teacher now

It doesn't in itself. It's just as likely that you think she's not a teacher. It depends largely on which part of the utterance is stressed. Here's one context:

Jane's a doctor? Is she really? I thought she was a teacher.

The past tense was matches the past tense of thought—the belief in the truth of the proposition 'she=teacher' was in the past. The speaker doesn't believe that anymore.

A different context:

Jane's a teacher? I thought she was a teacher. She acts like one.

Here the speaker uses the past tense for a similar reason—the thought/impression that 'she=teacher' was in the past, and now in the present it's confirmed to be true.