1：表示不受时限的客观存在
所谓不受时间限制的客观存在包括客观真理、格言、科学事实及其他不受时限的事实。
eg:
The earth rotates on its axis.
地球在其轴上旋转
Hydrogen is the lightest element.
氢是最轻的元素
A rolling stone gathers no moss.
滚石不生苔
London stands on the River Thames.
伦敦矗立在泰晤士河畔
2:表示现在习惯动作
所谓现在习惯动作指现在经常发生的动作，一般现在时常用来表示现在时间里某种动作的经常性和习惯性。
eg:
Percy often goes to his office by underground.
Father doesn't smoke.
He always sleeps with his windows open.
Mary usually learns languages very quickly,but she doesn't seem to be able to leran modern Greek.
上述用法的一般现在时常与频度副词连用。常见的频度副词有always,ever ,frequently,hardly ever,never,occasionally,often,rarely,seldom,sometimes,usualluy等。
频度副词通常位于主动词之前，如果主动词是be则通常位于其后，也可为了强调而位于其前。
eg:
The students (always)are always on time for class.
She (sometimes) is sometimes a little angry with him.
He hardly ever makes a mistake when he writes.
We rarely go hiking when it rains.
hardly ever 的含义是almost never,rarely 的含义是not usually.not ever=never
not always=sometimes it is the case and sometimes it is not ,not often=seldom
3:表示现时状态和现在瞬间动作
用一般现在时表示的现时状态通常带有一定的持续性，因此只适用于静态动词。
eg:
Someone's at the door,Carol.
What's the matter with you ?You look pale.
What do you think ,jane?
用一般现在时表示的现在瞬间的动作通常只适用于表示短暂动作的动态动词。这种动作转瞬即逝，几乎与说话时间同时起讫，甚至话音未落动作已经完成。
例如用在对快速体育运动的实况报道中
Harper passes the ball to Jennings,Jennings shoots and the goalkeeper leaps for it but-yes ,it's a goal
这一用法也常见于戏法表演。技术操作表演等得解说词中。
Look,i take this card from the pack and place it under the handkerchief
Now i put the cake mixture into this bowl and add a drop of vanilla essence
这一用法也常见于一些专门用于或日常用于中。
I declare the meeting open.
I wish you all a happy New Year
上述专门用语或日常用于一般都用第一人称。可做类似用法的动词还有agree,apologize,deny,name,object,promise,say,sentence,suggest,sympathize等
4：表示将来时间
第一种句型是在 I hope,I bet等后面的that-分句中可用一般现在时表示将来时间
eg:
I hope you have a good time.
I hope she likes the flowers.
在上述that-分句中，you have a good time =you will have a good time
she likes the flowers =she will like the flowers,两者可以交替使用
I bet it rains tomorrow=...it will rain tomorrow.
第二种句型是see(to it)/make sure /make certain+that-分句。
eg:
I'll see (to it)/make sure/make certain that you don't get lost.
在这里，you don't get lost 也是用一般现在时表示将来时间
第三种句型是由if/when 引导的条件分句和时间分句。
eg:
Will you go and help to get in the crops when the harvest time comes?
If it is fine tomorrow,we will go to the countryside.
这里的comes 和 is 不能改用will come 和 will be
