TYPICAL ERROR The students were assembled together in the hall.
CORRECTION The students were assembled in the hall.
EXPLANATION The word assembled means gathered together. To say assembled together is like saying gathered together together. Hence, together is a redundant (unnecessary) word after assembled.
Another form of redundancy occurs when words or concepts are repeated (often accidentally) in a sentence, as has happened in the following sentence:
It is clear that in today's society, unlike previous eras, that smoking in restaurants is not tolerated.
Sometimes, people redundantly use synonyms (words that mean the same) when trying to emphasise something, as in:
It is unpardonable and unforgivable for parents not to spend time with their children.
If emphasis is desired, that can be achieved by using words that convey different shades of meaning and degrees of intensity, such as in: It is reprehensible, if not unforgivable...