起先的英文：
at prime tense
to begin with

At first I couldn't perceive what he meant.
起先我不理解他说的意思。

I thought it would be fearfully quiet
我起先还以为它一定是个死气沉沉的地方哩。

She come initially to spend a few days,but in the end she stay for a whole month.
起先她只打算来待几天，但后来却住了整整一个月。

We first saw smoke rising up in the valley, then the rocks and mud gushing out.
我们起先看见山里起了烟，然后泥沙就挟着石块儿一下子涌出来了。

To begin with, we had little support, but later on people began to rally to us
起先支持我们的人很少，后来人们就开始聚集在我们一边了。

She was very formal at first,but then she unbent a little and told a joke.
她起先显得很正经，但后来变得随和些，还讲了个笑话。

This is a prime problem.
这是一个有关质数的问题。

This is the prime ratio of the nascent increments
这是最初增量的最初比。

The prime of the year has begun.
春天来了。

progressive tense
ph.1. 【语】进行时态,进行式

The tense used is decided by the subject.
所用的时态取决于主语。

A verb form in the present tense.
现在时态的动词形式

It is beginning to dew.
在结露水了。

The scrambling begins.
混乱开始了。

The days are beginning to shorten.
白天开始变短了。