1) The Sahara is the biggest desert in the world.
形容词最高级前通常必须用定冠词 the，副词最高级前可不用。
形容词most前面没有the，不表示最高级的含义，只表示"非常"。
It is a most important problem.
=It is a very important problem.
注意： 使用最高级要注意将主语包括在比较范围内。
(错)　Tom is the tallest of his three brothers.
(对)　Tom is the tallest of the three brothers.

2) 下列词可修饰最高级，by far, far, much, mostly, almost
This hat is nearly / almost the biggest.
注意：
a.　 very可修饰最高级，但位置与much不同。
This is the very best.
This is much the best.
b.　 序数词通常只修饰最高级。
Africa is the second largest continent.

3) 句型转换：
Mike is the most intelligent in his class.
Mike is more intelligent than any other students in his class.

4) "否定词语+比较级"，"否定词语+ so… as"结构表示最高级含义。
Nothing is so easy as this.
=Nothing is easier than this.
=This is the easiest thing.