Adjectives and adverbs

Adjectives and adverbs are used to perform different functions in phrases and sentences. Adjectives are used to modify nouns and to ascribe properties to the subject or object of a clause, whereas adverbs are used to modify adjectives and adverbs. Adverbs also function as adverbials at the clause level.

It is common in informal spoken English to use adjectives in adverbial functions. However, in formal writing this usage is not appropriate. Thus, the use of adjectives in examples like the following are characteristic of informal speech and would be regarded as errors in a formal written context (and also in careful speech):

(1) You must be real careful not to touch the wire. [In academic writing, the adverb really would be used to modify the adjective careful]

(2) Bill performed the task good. [In academic writing the adverb well would be used to fulfil the role of manner adverbial] 

A Swedish perspective: Adjectives after certain verbs in English (click to expand/contract)

Verbs that refer to sensory perception, e.g. look, feel, taste, sound and smell are always followed by adjective phrases in English, whereas in Swedish, some of the corresponding verbs are followed by adjective phrases, and others by adverb phrases. Note especially the verbs smell and taste, which behave differently in English and Swedish.

Adjective phrase in English

Adverb phrase in Swedish

The strawberries smelt strange.

Jordgubbarna luktade konstigt.
Jordgubben luktade konstigt.

The strawberries tasted good.

Jordgubbarna smakade gott.
Jordgubben smakade gott.

Note: Adjectives, but not adverbs, have both singular and plural forms in Swedish. Thus, with a verb like verka, a following adjective phrase agrees with the subject: Jordgubben verkade konstig. vs Jordgubbarna verkade konstiga.