Let s look at each of these in turn. The topic sentence explains the topic of the paragraph and it is usually best to place this sentence at or near the beginning of the paragraph. A good paragraph has unity, which means that it deals only with one subject and does not wander from topic to topic. Coherence in a paragraph is related to unity and refers to the bridges or links between sentences. These links may be logical or verbal.
Logical links carry the same idea from sentence to sentence.
The use of parallel sentences is also a logical bridge. Verbal links can be made by repeating a key word or phrase in each sentence. In addition, synonyms can be used in each sentence to link them together. Pronouns can also be used in one sentence refering to a word in another sentence in order to link 2 sentences together in the same paragraph. Those that give a successful results in the treatment of the patient are the most rewarding.