这两词既可做实义动词用,又可做情态动词用.作为情态动词,两者都只能用于疑问句,否定句和条件句. need 作实义动词时后面的不定式必须带to,而dare作实义动词用时, 后面的to 时常可以被省略.
一、 need的用法
1) need可用作实义动词,意为"需要；必要",后面可接名词、动名词或动词不定式等作宾语.注意"need doing"表示被动意义,相当于need to be done.例如：
I need a dictionary, so I need to go to the bookstore. 我需要一本词典,因此我要去趟书店.
How often does your hair need washing(need to be washed)? 你的头发需要多久洗一次?
2) need可用作情态动词,通常用于疑问句和否定句中,后接动词原形.这时need没有人称和数的变化,也没有时态的变化.例如：
It's only eight o'clock. Need you go so early? 才八点.你需要去这么早吗?
You needn't tell him about it as I have told him. 你不必跟他说那件事,我已经告诉他了.
3) needn't do与needn't have done的区别：
两者都表示"不必做.".但前者表示现在或将来不必做；而后者表示"过去(本来)不必做(而事实上已经做了)".例如：
You needn't carry the desks out of the classroom when you clean the classroom. 你打扫教室时不必把桌子搬到教室外.
You needn't have bought such a big TV as it takes too much room. 你本来不必买这么大的电视,它占据的空间太大了(而事实上已经买了).
二、 dare的用法
1) dare用作实义动词,此时其后的动词不定式可带to也可不带to,且dare有人称和数以及时态的变化.例如：
I dare to jump down from the top of the wall. 我敢从那墙头上跳下来.
She doesn't dare (to) meet her teacher's eyes. 她不敢与老师对视.
2) dare用作情态动词,后跟动词原形,主要用于疑问句、否定句和条件句中.例如：
How dare she do things like that to me? 她怎么敢对我做那种事?
-Dare you catch the mouse? 你敢去抓那只老鼠吗?
-I daren't do that. 我不敢抓.
If you dare say that to our teacher, I would vote for you. 如果你敢向我们的老师说那件事,我就投你一票.
希望以上答案对你有帮助,Good luck to you:)