Building Vocabulary

What are Contractions?

Since the word 'contract' means to shorten or squeeze together, it seems logical that a contraction is two words made into one by putting an apostrophe where letters have been omitted. 
Words like can't (can + not), don't (do + not), and I've (I + have) are all contractions.

Compound Words

A compound word is a word which is made up of two or more words that have a single unit of meaning. For example: fireworks, basketball, full moon, etc. 

What are collocations?

A collocation is a group of words that usually go together. For example, in English, we usually say 'heavy rain'. It's correct grammatically to say 'strong rain' or 'big rain', but both of these sound completely strange. A native English speaker would never say 'big rain'. If you use the normal collocation ('heavy rain') your English will sound a lot better and more natural and it will be easier for native speakers to understand you. Collocations are very, very important.