We're using a comma there, because the " If clause" comes first.

我们在那里使用逗号，因为 if 子句先出现。

The " If clause" comes second, so there's no comma.

If 子句在第二个，所以没有逗号。

If the " If clause" comes first, we need a comma, if it comes second, we do not.

如果 if 子句在前，我们需要逗号，如果它在后，我们就不需要逗号。

Now, what about the if clause?

那么，if 从句呢？

Each conditional sentence has an if clause, and a main clause.

每个条件句都有一个 if 子句，和一个主句。

Notice we use the present tense in the if clause.

注意我们在 if 从句中使用现在时。

We use a present tense in the if clause.

我们在 if 从句中使用现在时。

We often call them " if clauses" because they often begin the same way.

我们通常称它们为“if从句”，因为它们通常以 if 开头。

It has two parts: the condition (if clause) and the result (main clause) .

条件（if 子句）和结果（main 子句）。

The " if" clause can go at the beginning of the sentence, or in the middle.

“If” 从句可以放在句首或者句中。

One is in the if clause, and one is in the main clause.

一在 if 子句中，一个在主句中。

So our 'if' clause is happening in the past, right?

我们的“if”从句是发生在过去，对吧？

We have an 'if' clause and a main clause.

有一个“if”子句和一个主句。

The 'if' clause and the main clause.

“if”子句和主句。

We still have a hypothetical past action in the 'if' clause and the hypothetical present result in the main clause.

我们在“if”子句中还是有一个假设的过去行为，而假设的当前结果在主句中。

Or we could say the if clause at the end.

或者我们可以在最后说 if 子句。

There are a few basic patterns for the 'if clause'.

“if 子句” 有一些基本模式。

So, that's the past perfect with the " if" clause, okay.

所以，这是带有“if”从句的过去完成时，好吧。

Don't forget to put the comma in after the 'if' clause.

不要忘记在“if”子句之后加上逗号。

A conditional sentence can start with the if clause, or the result clause.

条件句可以以 if 子句或 result 子句开头。