a minute later 一分钟后，属于副词用法

A minute later he excused himself and left the room.  

一分钟之后，他说了声抱歉就离开了房间。

Half a minute later she came in the front door.  

半分钟之后，她就从前门进来了。

Herry came in a minute later.  

一分钟后,亨利进来了.

later 副词用法“后来；以后；过后”

He resigned ten years later. 

10年后他辞了职。

I'll join you later. 

我呆会儿和你会合。

later 形容词用法(1)“后来的；以后的”

At a later news conference, he said differences should not be dramatized. 

在后来的新闻发布会上，他说不应夸大分歧。

The competition should have been rescheduled for a later date. 

比赛本应另择日期。

later 形容词用法(2)“晚年的；后期的；末期的”

He found happiness in later life. 

他在晚年找到了幸福。

In his later years he wrote very little. 

晚年他甚少动笔。

ahead of  在…之前

Mark was out of earshot, walking ahead of them.  

马克走在前面，听不见他们的声音。

The election was held six months ahead of schedule.  

选举提前了6个月举行。

Henry generally stayed ahead of the others in the academic subjects.  

亨利的文化课成绩通常都优于其他学生。

The Prime Minister was speaking ahead of today's meeting.  

首相在今天的会议开始之前作了发言。

The Socialists may still finish ahead of the pack.  

社会党最终仍可能会领先。

We have a very busy day ahead of us today.  

今天迎接我们的将是非常忙碌的一天。