- You may know a word only when it is in helpful context.
- You may know generally what a word means, but not know its nuance.
- You may know one sense of a word, but not another.
- You may know a word when you see or hear it, but never think to use it yourself.
We learn so many words, we couldn't possibly be taught all the words we know or even look each of them up in a dictionary. Instead, most are learned naturally through repeated contextual encounters.
After the 4th grade, the vast preponderance of vocabulary is learned incidentally while reading. Indeed a common refrain in education literature is that the single most important thing you can do to improve students' vocabularies is to get them to read more. Even children's books tend to have more rare words than the typical conversation of two
Learning new words for already understood concepts is much easier than when concepts are also new. Learning a new concept can be very demanding, but also highly useful to facilitate thought and communication.
However hard or easy a word is to learn, many people find a non-linguistic representation exceedingly helpful. For example, the word translucent might best be learned while looking at pictures of translucent objects; or concerto might be learned while listening to a piano concerto.
People who are aware of and interested in words tend to learn them better. Of course, encountering a word more frequently or seeing value in knowing the word increases the probability of learning it.