Adjectives: forms

from English Grammar Today

Unlike in many other languages, adjectives in English do not change (agree) with the noun that they modify:

All new foreign students are welcome to join the clubs and societies.

Not: All new foreigns students …

Every room was painted in different colours.

Not: … in differents colours.

Identifying adjectives

There is no general rule for making adjectives. We know they are adjectives usually by what they do (their function) in a sentence. However, some word endings (suffixes) are typical of adjectives.

suffix	examples
-able, -ible	comfortable, readable, incredible, invisible
-al, -ial	comical, normal, musical, industrial, presidential
-ful	beautiful, harmful, peaceful, wonderful
-ic	classic, economic, heroic, romantic
-ical	aeronautical, alphabetical, political
-ish	British, childish, Irish, foolish
-ive, -ative	active, alternative, creative, talkative
-less	endless, motionless, priceless, timeless
-eous, -ious, -ous	spontaneous, hideous, ambitious, anxious, dangerous, famous
-y	angry, busy, wealthy, windy

Warning: 

Adjectives ending in -ic and -ical often have different meanings:

The economic policy of this government has failed.

A diesel car is usually more economicalthan a petrol one.