vocabulary
All the words you know and use.
context
The words and sentences around a word. They give clues about its meaning.
word family
A group of words built from the same base, like play, player, playful and replay.
homograph
Words that are spelled the same but have different meanings, and sometimes different sounds, like wind (air) and wind (turn).
homophone
Words that sound the same but have different spellings and meanings, like two, too and to.
glossary
A small dictionary at the back of a book. It explains the special words in that book.