Words which connect words, phrases, clauses or sentences are called conjunctions (see
"to conjoin" = join, unite). The most common ones are 'and', 'or' and 'but'. These words
all have different nuances and connotations but they all help to build up meaningful
relationships within a sentence.
Conjunctions
Cohesive Devices: A variety of useful English Conjunctions exists, which complete this
list of the most used Cohesive Devices. Together, they can help to express a cohesive
view and easy understandable and readable texts.
    There are three basic types of conjunctions:
Definition: Coordinating conjunctions are used to connect two independent clauses
Subordinating conjunctions are used to establish the relationship between the
dependent clause and the rest of the sentence
Correlative conjunctions are used to join various sentence elements which are
grammatically equal
Coordinating Conjunctions: Comes usually in the middle of a sentence, and
a comma is used before the conjunction (unless both clauses are very short). They join
individual words, phrases, and independent clauses. 
Whereas coordinating conjunctions join parts of a sentence, the purpose of transitional
words and phrases usually is to join two 'sentences'.
Examples: 
We can draw lessons from the past, but we cannot live in it.
The purpose of most computer languages is to lengthen your resume by a word and a
comma.
    And, but, for, nor, or, so, and yet — are the seven coordinating conjunctions. To
    remember them, the acronym FANBOYS can be used.
      1.  F = for
      2.  A = and
      3.  N = nor
      4.  B = but
      5.  O = or
      6.  Y = yet
      7.  S = so
Subordinating Conjunctions
    Also called subordinators, introduce a dependent clause. These adverbs that act
    like conjunctions are placed at the front of the clause - and a comma is needed at
    the end of the adverbial phrase when it precedes the main clause. 
         Examples: 
         If the only tool you have is a hammer, you tend to see every problem as a
         nail. [Abraham Maslow]
         Some people make headlines while others make history. [Philip Elmer-
         DeWitt]
     
    ConjunctionsConcession
       though
       although
       even though
       while
    ConjunctionsCondition
       if
       only if
       unless
       until
       provided that
       assuming that
       even if
       in case (that)
       lest
    ConjunctionsComparison
       than
       rather than
       whether
       as much as
       whereas
    Conjunctions Time
       after
       as long as
       as soon as
       before
       by the time
       now that
       once
       since
        till
        until
        when
        whenever
        while
      
     Conjunctions Reason
        because
        since
        so that
        in order (that)
        why
     Relative Adjective
        that
        what
        whatever
        which
        whichever
         
     Relative Pronoun
        who
        whoever
        whom
        whomever
        whose
         
         
     ConjunctionsManner
        how
        as though
        as if
     Conjunctions Place
        where
        wherever
Correlative Conjunctions
    They are always used in pairs and denote equality; and show the relationship
    between ideas expressed in different parts of a sentence - and thus make the joining
    tighter and more emphatic. When joining singular and plural subjects, the subject
    closest to the verb determines whether the verb is singular or plural. 
     
       as . . . as
       just as . . . so
       both . . . and
       hardly . . . when
       scarcely . . . when
       either . . . or
       neither . . . nor
        
       if . . . then
       not . . . but
       what with . . . and
       whether . . . or
       not only . . . but also
       no sooner . . . than
       rather . . . than
Conjunctive Adverbs
    They are often used as a linking device between ideas. They show logical
    relationships expressed in clauses, sentences or paragraphs.
    Conjunctive adverbs are very emphatic, so they should be used sparingly.
     
    Similar to And
        
       also
       besides
       furthermore
       likewise
       moreover
    Similar to But
        
       however
       nevertheless
       nonetheless
       still
        
       conversely
       instead
       otherwise
       rather
    Similar to So
        
       accordingly
       consequently
       hence
       meanwhile
       then
       therefore
       thus