When you say you know a word or phrase, you could mean one of two things. First, you could mean that if someone says the word to you, you know what it means. This is passive knowledge. The second way of knowing is that you can recall and use that vocabulary appropriately. This is active knowledge.
This isn’t anything to do with active or passive voice in grammar. It’s about how you store your memory of a word for later use, and there’s a large, important difference.
The difference between passive and active vocabulary
With passive vocabulary, you can listen and understand. Hearing the vocabulary used prompts you to recall its meaning. In other words, you are being made to recall it. So it’s passive vocabulary.
Active vocabulary, on the other hand, is vocabulary that you can recall and use at will when the situation requires it. You are choosing to use the word and actively retrieving it from memory.
One of our teachers in first year had a great analogy for this. He showed us a £5 note and asked us what it was. Of course everybody recognised it. Then he asked us to describe a £10 note in detail.
Very few of us could come up with much. We knew it had the queer old dean dear old Queen on it, and a couple of people remembered that Charles Darwin is on the back.
But beyond that we came up with nothing, despite seeing £10 notes regularly (although not as regularly as we might like, and never for very long). This is the difference between active and passive knowledge. It’s whether you can merely recognise something, or actually reproduce it from memory.
Isn’t this obvious?
Thanks to Olle for making this point.
If you find this distinction a bit obvious, then good for you. However, I don’t remember really acknowledging the distinction until that teacher pointed it out explicitly. Before that I’d been vaguely aware of it, but not enough to act on it when learning.
It’s particularly important in the early stages of learning a language, before you can start to acquire vocabulary and improve naturally. As a beginner, you’re trying to cram in vocabulary as rapidly as possible, to propel you to higher levels. This is when it’s easy to get a lot of passive vocabulary whilst neglecting the active side of things.
This is probably a familiar experience
It’s easy to forget or ignore this significant difference when you’re learning words. As language learners, we often mistakenly think that we ‘know’ a word because we have no trouble understanding it when other people use it. But when speaking, how often do you find yourself talking around vocabulary that you can’t recall quickly enough?
It’s not necessarily that you can’t recall the word at all. Maybe with a couple of seconds’ thought you’d remember it. That’s not a long time, but it’s often too long in the middle of a conversation. The word is in there, it’s just you can’t directly recall it. It needs prompting to come out, so it’s passive vocabulary.
My own example
An example for me is the word 舞池 (dance floor) in Chinese. If I see or hear it I get an image of a dance floor without any difficulty. But if I was in the middle of saying something and wanted to talk about a dance floor, I think I’d most likely say “the place where people dance”.
That’s not necessarily a bad thing - being able to get your point across on the spot is an important ability for language learners. When your ultimate goal is to speak like a native, though, you’ll probably want to get to the point where an apt word does just roll off your tongue.
Why this is so important for language learners
Simply being aware of this distinction can make a huge difference in your learning. If you’re not aware that passive and active vocabulary are very different things, there’s a risk that you’ll become one of the many people who can read and listen to a language very well, but can speak or write very little of it.
Using flashcards for both directions in SRS (recognition and production) is important. Finding ways to engage actively with your studies is important (trying to teach or explain your target language is a good one). Getting out and using language in context is important.
It’s this context that will help create active vocabulary. The first time you encounter the situation, you perhaps can’t recall the words fast enough. But you then come to associate those words with that context, and the _next _time they’ll be there waiting.