WORD-BUILDING is the process of formation, construction or composition of different words.
In English it is always easy to make several new words from a particular root word. You can easily make it’s NOUN, VERB, ADVERB, ADJECTIVE, OPPOSITE, SYNONYM etc. using your language skill. Suffixes and Prefixes can also be easily added to make meaningful words.
For example, let’s take a word free, which is an adjective. We can change the word in different forms, freedom (Noun) to free (Verb) freely (Adverb) bound (Antonym) independent (Synonym)