Adverbs are words that modify adjectives, verbs, and other adverbs.
True adverbs, such as أَمْسِ or هُنا, are indeclinable, meaning they do not change their forms.
In addition to true adverbs, Arabic has adverbial accusatives formed from nouns and adjectives.
Adverbs of time ظَرْفُ الزَّمانِ
سافَرْتُ مَساءً I traveled in the evening.
مَساءً "Evening" defines the time of the travel.
Adverbs of place ظَرْفُ الْمَكانِ
جَلَسْتُ تَحْتَ الْمِظَلَّةِ I sat under the umbrella.
تَحْتَ الْمِظَلَّةِ "Under the umbrella" defines the place of sitting.
Other examples:
أَمامَ (in front of)
خَلْفَ (behind)
فَوْقَ (above)
See also: