0 used especially in writing before a piece of information that makes the meaning of something clearer or shows its true meaning:
1 abbreviation for id est (= Latin for "that is"):
2 used to mean "that is" before you give a more detailed explanation about something that you have just written:
The new payroll system will apply from the first payment in the forthcoming tax year, i.e. April.
For all churches decorous dress is required, i.e. no shorts, bare shoulders, etc.