THREE UNITS

Synonyms:

It´s important to use synonyms to make the reading more interesting and varied.
the accurecy of synonyms is always depending on context.
You may use synonyms to express a word in an academic context for example, or an informal context.
Example: The word "Pupil" can be used in a school ,but in Univesity the word student is used more often.Or the word "teacher" can be used in school but in an important Conference ,or University ,the word "Professor" is used more often.
Some examples of synonyms: Goal- Target
                                                 Controversy-Argument
                                                 Behaviour-Conduct
                                                 Interpretation-Explantion
                                                 Large- Big.
Link: http://www.k12reader.com/synonyms-and-antonyms/
Cohesion:

Cohesion is linking phrases so as to make the text clearer and more readable.
The use of conjunctions is often used to unite sentences or you can use words like: "he,his,they,it and that" to refer back to something mentioned before.

Example: The President flew his helicopter to the Presidential Palace, for it was easy to pilot.
The word his refers to the President.  The word it refers to helicopter.

Other words can be used as cohesion  like possesive pronouns: her-hers-their-theirs
                            objective pronouns: her-him-them
                            demostrative pronouns: this-that-these-those
                            phrases like:  the former-the latter-the first-the second.


Link:http: //www.slideshare.net/cupidlucid/cohesion-in-english-presentation



Comparisons:

Ther are two ways of comparing things when writing:
Example: John is taller than Mike.
                She is more beatiful than her classmates.

1.Er is  added to one syllable adjectives: fast-faster and two syllable adjectives ending in y: pretty-pretier.
2. More is used with two syllable words:beatiful-more beatiful
There are, however, two syllable words that can be used in either form: simple-simpler-more simpler.

To make comparisons more exact you can use words like : Considerably,Slightly and Significantly for example:
 It rained considerably stronger than expected.
 The car is slightly more silent than the truck.
 She is significantly smarter than her sisters.

Link:http://www.english-at-home.com/grammar/comparisons/