(used after a word or phrase which is going to be explained) that is; which means
that is
Cases of word usage
1) statement that seems to say something opposite to common sense or the truth but that may be true, e.g. 'More haste, less speed', i.e. if you hurry too much, you may find you take longer (paradox)
2) one of the four main divisions of the year, i.e. spring, summer, autumn, winter; to add salt, pepper etc to (food) to improve the taste; to make (wood) suitable for use by leaving it to dry (season)