adjectives used as a noun 
We translate this in English by using the word "one" with the adjective:
- laica "a keen one"; i laica "the keen one"
- carnë "a red one"; i carnë "the red one"
- hwarin "a crooked one i hwarin "the crooked one"
In this case the adjective is inflected with the noun endings:
- laicar "keen ones"; carni "red ones"; hwarindi "crooked ones"
Dual and partitive plural are also possible:
- laicat "a pair of keen ones" carnit "a pair of red ones"; i hwarindu "both crooked ones"
- laicali "some keen ones"; carnili "some red ones"; hwarindeli "some crooked ones"
These nouns can of course take all case endings, e.g.
- laicaron (genitive plural); carnillo (ablative singular); i hwarindun (dative dual) ...
adjectives following the noun 
When the adjective is put behind its noun, the rule of the last declinable word applies. This means that the adjective takes the case endings and the noun loses them:
- coa carninna "to a red house" (allative)
- coa carnillo "from a red house" (ablative)
In the plural the adjective has the plural case-endings and the noun is in the nominative plural:
- coar carninnar "to red houses" (allative)
In the dual the adjective has the dual case-endings and the noun is in the nominative dual:
- coat carnilto "from a pair of red houses" (ablative)
Note: adjectives only have t-duals even if they contain a d- or t-sound:
- i aldu tiucatsë "in both thick trees" (locative)
The other types of words that are inflected in this way are:
- participles when they follow the noun (see Verbal forms)
- demonstrative pronouns
- titles also always follow the noun, so it is also the title and not the noun itself that is inflected:
- Elendil Voronda "Elendil the Faithful"
- Elendil Vorondan "to Elendil the Faithful" (dative)
- Elendil Vorondallo "from Elendil the Faithful" (ablative)
But there are two cases in which this rule isn't followed:
- When the noun is in the partitive plural, the case ending remains with the noun and the adjective has its original (plural) form:
- coalissë carni "in some red houses" (locative)
- The adjectives on –ëa only have a plural form and no other cases so the ending remains with the noun:
- coanna laurëa "to a golden house" (allative)
- coannar laurië "to golden houses" (allative)
A few remarks:
- The forms of the plural can only be used when the adjective follows the noun, not when it is used as a noun. But in that case it follows the ordinary rules of Neo-Quenya/Declension Paradigms.
- Adjectives on -ëa cannot be inflected so they aren't included in these tables. They can be used as nouns but in that case they are inflected like the nouns ampa "hook" or alda "tree".
- The partitive plural can only be used when the adjective is used as a noun so it isn't included in the table.
Adjectives on -a (but not -ëa) are inflected as follows (anda "long"):
Adjectives on -ë are inflected as follows (ninquë "white"):
Adjectives on -n are inflected as follows (melin "dear"):