Read this tip to make your life smarter, better, faster and wiser. LifeTips is the place to go when you need to know about Building Vocabulary and other Learning Languages topics.
There are several ways to try and answer this question, but most studies seem to indicate that if you know between 2,000 and 3,000 word in a given language you can function in most any environment. Some of the better studies conducted by teachers of ESL (English as a Second Language) show that foreign students who acquire a vocabulary of the 2,500 most commonly used words in English can handle any university-level academic text. The percentage of technical terms they encounter is less than 1% of the total vocabulary, and even their native English-speaking classmates will probably need to look up many of those words. Once your vocabulary reaches a certain size, you can pick up words by context, or if someone tells you the definition, you'll know enough to understand it. The goal is to acquire a big enough vocabulary that it can build itself.