Hi, Izzat Hannah,
What is the difference between used to and the past simple tense in these two examples?
1- I used to have a cat.
2- I had a cat.
I would add 'once' to 2: 'I once had a cat'. I see that both refer to a past state and mostly have the same meaning. However 'used to' sounds to indicate a longer state. If you changed the subject, there could be another subtle difference.
- He used to have a cat. = He no longer has that cat.
- I met John last year. He had a cat and said ..... (It is not clear whether he still has that cat or not).