Although the words afraid and frightened have similar meanings, the grammar is not the same. These are all adjectives and express nearly the same degree of fear. In many cases, they are interchangeable.
Frightened /Adjective/ (ভীত / সন্ত্রস্ত):
Frightened is mainly used to talk about a sudden fear. The uses are – only ‘frightened’ or frightened + noun / frightened of / frightened to / frightened by.
Example:
Afraid /Adjective/ (ভীত / শঙ্কিত):
Afraid is not normally used before a noun. It goes after the verb. The uses are – only ‘afraid’ / afraid of / afraid to.
Example (can be interchanged with frightened):