1. unnecessarily的意思是“不必要地”，强调“多余”“过于”“多此一举”“完全没有必要”。注意体会：

He accused her of being unduly harsh. 他指责她太过苛刻。

You do worry unnecessarily, you know. 你应该明白，你的担心纯粹是多余的。

The instructions are unnecessarily complicated. 这些用法说明过于复杂，没有必要。

We do not want to prolong the meeting unnecessarily. 我们不想不必要地延长开会时间。

The report paints an unnecessarily bleak picture of the town. 这份报道把这个镇子描绘得过于惨淡。

2. not necessarily 的意思是“不一定”“未必”，暗示某种结果或结局并非不可避免，但它也完全可能发生。注意体会下面的例句：

Biggest doesn't necessarily mean best. 最大的不一定是最好的。

Wealth is not necessarily synonymous with happiness. 财富未必等同于幸福。

Seats in the front row are not necessarily the best. 前排座位不一定就是最好的。

The more expensive articles are not necessarily better. 较贵的东西不见得就较好。

Expense does not necessarily indicate worth. 费用未必能反映价值。

A wasp or bee sting is painful but not necessarily serious. 被黄蜂或蜜蜂蜇一下疼是疼，但未必碍事。

Having this disease does not necessarily mean that you will die young. 得了这种病不一定就活不长。

Going to the dentist need not necessarily be a painful experience. 去看牙医未必就是件痛苦的事。

Some economists have pointed out that low inflation is not necessarily a good thing. 一些经济学家指出，低通货膨胀不一定是好事。

Headings within the text should be bold but not necessarily bigger. 文章中的标题应该是黑体，但不必是更大的字体。