-ce
important - importance
patient - patience
violent - violence

-ity
popular - popularity
fomp3al - fomp3ality
regular - regularity

-ness
happy - happiness
lazy - laziness
ruthless - ruthlessness

-y
difficult - difficulty
modest - modesty
honest - honesty

Some spelling rules:（拼字的规则）

When the adjective or noun ends in –e, -t or –y, sometimes its spelling changes.
For example:
-e
nature - natural
fame - famous

-t
important - importance
patient - patience

-y
happy - happiness
lazy - laziness