Student or Learner
Can I use ' might have pp' instead of ' could have pp' to indicate the same meaning for the following sentence?
My housemate had time to wash the dishes last night, but she went out instead.
_> he/ she could have washed the dishes last night or
->He/she might have washed the dishes last night or
-->He /she may have washed the dishes last night.
In your sentences above, 'might have' and 'could have' might/could have very similar meanings. Both 'could have washed ...' and 'might have washed ...' could mean 'it is possible that she washed ...' . However, 'could have' could mean 'would have been able to', which 'might have' cannot. We need more context to be absolutely sure.