Find the centre
A root is the central meaningful part of a word. In help, helpful and helpless, the shared root is help.
The University of Ottawa’s word-formation guide explains how beginnings and endings can be added around a root. The family resemblance is in the part that stays.
Keep the help
Imagine someone offering help. Helpful describes a person or thing that gives it. Helpless describes someone unable to help themselves.
The ending changes the meaning, but help remains visible. The same approach lets you spot play inside replay and playful. These are small examples you can take apart without needing a dictionary of Latin.
Some roots need company
Not every root is a complete everyday word by itself. The SIL linguistic glossary calls these bound roots: roots that need other pieces attached. Glasgow’s grammar guide separates roots from attached affixes.
For now, practise with clear families such as help, play and kind. Next, put a piece at the front: meet the prefix.