Suffixes change word class, e.g. from verb to noun or noun to adjective, but they can also change meaning (see sections B and C below).
Noun or verb + suffix
Note: Sometimes there is a spelling change. Here are common examples:
double the consonant, e.g. sun/sunny, fog/foggy
leave out the final ‘e’, e.g. create/creative, fame/famous
leave out the final ‘s’ before ‘al’, e.g. politics/political; economics/economical change ‘y’ to ‘i’ before ‘al’, e.g. industry/industrial
This suffix (also -ible in some words) is used to form many adjectives from nouns or verbs: enjoyable, comfortable, knowledgeable (= knows a lot), suitable (= right/correct for a particular situation).
Quite often, -able (and -ible) has the meaning ‘can be done’. For example, something that is washable ‘can be washed’. Other examples include:
drinkable, comprehensible (= can be comprehended or understood), reliable (= can be relied on or trusted, e.g. a car or other machine that never goes wrong or breaks down).
Words ending -able quite often express the opposite meaning by adding the prefix un-: undrinkable, unreliable, unbreakable (= cannot be broken), unsuitable, uncomfortable Words ending -ible add the prefix in-:
incomprehensible, inflexible (somebody who is inflexible has a fixed idea about something and cannot change quickly or easily; an inflexible timetable cannot be changed easily); inedible (= cannot be eaten).
-ful and -less
The suffix -ful often means ‘full of’ + the meaning of the adjective: careful, you are full of care; if you are helpful you are full of help. Other examples are: painful (= hurts a lot), useful, and thoughtful (= someone who is thoughtful is kind and always thinks about others; a thoughtful action shows care for others)
The suffix -less means ‘without’ + the meaning of the adjective: if you are careless, you do something ‘without care’. Other examples are: painless, useless (= has no use or function) thoughtless, jobless and homeless (= with nowhere to live)
Note: You can see that -ful and -less are often used with the same words to form opposites. This is not always true: a person with a home is NOT homefttl.