Nowadays there are so many dictionaries on various subjects. Making sure that your dictionaries are reliable is very important (especially in science and technology discipline). Before I use a dictionary as my tool, I would check its reliability first. How to? First just choose some words at random (of course, they are words that I know and typical in the certain field that I’m interested) and look them up. If wrong results come, no more chance for that dictionary. If the first step goes all right, I would go on to select a random page and check it. Even after these steps, it is still advisable to turn to other resources for an alien word if you feel something wrong.  (来源：专业英语学习网站 http://www.EnglishCN.com)

There are indeed some famous publishers whose dictionaries are quite authoritative. Choosing their products would be safe and could save us some time. Though someone say they would buy one with multilingual expressions or so. It would be better to get one whose edition way comforts your eyes. Good feeling is always important in work.

On-line dictionaries are good complements. But you need enough background knowledge to use them. And when dictionaries are not enough, turn to encyclopedias. This is proper when you encounter some news words just being born.

Reliable and friendly assistant could help much in our work. Choosing good dictionaries is just like employing good assistants. Prudence is needed.