Lexicon
THE WORD STOCK OF A LANGUAGE IS SAID TO BE ITS LEXICON. Lexicon and grammar combine to make syntax.
English is distinctive for its large number of loan words, particularly from Romance languages. In general, scientific terms (such as "precipitation") come from Latin or Ancient Greek, while their more basic alternatives (like "rain") have a Germanic origin.
Many musical terms in English derive from Italian (say "coda").
How to Boost Your Vocabulary
REPEATING NEW words and phrases multiple times helps to solidify them in your memory. Using flashcards with the word on one side and its translation on the other can be a helpful tool for memorizing new vocabulary. Try to learn new lexicon in context, by seeing them used in sentences or reading material. This can help to build a better understanding of how the word is used.
Our passive vocabulary is always larger than our active one -- that is true for native speakers as well as learners. Nonetheless, actively using new words and phrases in speaking and writing helps with retention and reinforces the connections between the words and their meanings. Another tip is to associate new vocabulary with words you already know, or with visual cues. If you think in a visual way, mind maps are useful. In fact, the human brain is structured like a mind map, not a list of items.
You will find that each word you learn is connected to many other words, and once you understand the rules, you can combine them to create new terms. From the root "rain" comes "rainfall", "rainy", "rainbow" and so on. One could imagine that "rain" and "fall" are two neurons with a synapse linking them. Build two more synapses to the root "water" and then "rainwater" and "waterfall" are possible.