Theorie:

We can make adjectives from nouns or verbs with the suffixes: -ful; -less; -ive; -ing; -ian and others.
Be careful! Sometimes the spelling changes when you add a suffix.

Here are some of the possible suffixes:
 
Suffix
Examples
-able, -ible
admissible, possible, probable, reasonable
-al
global, final, special
-ant
resistant, resultant
-ar
perpendicular, popular, regular, similar
-ed
interested, limited, related
-ful
harmful, useful, successful
-ic, -ical
atomic, basic, mathematic(al), economic(al)
-ive
active, illustrative, indicative, sensitive
-less
harmless, helpless, hopeless
-ory
introductory, preparatory, satisfactory
-ous
porous, serious, various
-y
busy, easy, early, happy, healthy
-ing
interesting, depressing, exciting
 
Suffixes often change the meaning of the word:
  
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This kitten is harmless
This cat is harmful