later
later和later on都可以用，如That happened later (on) 和I shall call again later (on)。注意不可从现在算起说明若干时间而用later，如不可说I shall call again a week later，该把a week later改作in a week。
下面各句里的a week later都不是从现在算起，所以用得不错：
- I called on him on 24 July, and called again a week later.
- I shall call on him on 20 October and shall call again a week later.
- When you see him for the first time, you may think him rather inaccessible, but when you see him again a week later you are likely to find him quite likable.
As you have some extra work to do today, you'll have to leave the office an hour later里的an hour later作“比平时（或比原定计划）迟一小时”解。
