Conjunction (कंजंक्शन)
समुच्चय बोधक अव्यय
Conjunction is the word or set of words that joins two words or two sentences.
समुच्चय बोधक अव्यय (Conjunction) वह शब्द या शब्दों का समहू है जो दो शब्दों या वाक्यों को जोड़ता है.

1.
Two and two make four
2.
I like to study but he likes to play.
3.
Give the book either to me or to him after reading.
4.
Please come home as soon as you complete your examination.
Relative pronouns, relative adverbs and prepositions also join words and sentences, hence care has to be taken while classifying them into the different parts of speech.
Conjunctions की ही तरह relative pronouns, relative adverbs और prepositions भी शब्दों या वाक्यों को जोड़ने का काम करते हैं इसलिए इन्हें अलग अलग चिह्नित करते समय सावधानी बरतना ज़रूरी है.
Classification by Form - रूप आधारित वर्गिकरण
Correlative Conjunctions
Some conjunctions are used in pairs, like this...
कुछ conjunctions को शब्दों के जोड़ों में प्रयुक्त किया जाता है, जैसे...

Either....or
Neither....nor
Both....and
Between....and
Though....yet
Whether....or
Not only .... but also
Conjunctions used in such pairs are referred to as correlative conjunctions.
इस प्रकार pairs में उपयोग किये जाने वाले conjunctions को correlative conjunctions कहते हैं.

Compound Conjunctions
Often we use compound expressions as conjunctions; such expressions as called compound conjunctions.
हम बहुत से compound expressions का उपयोग conjunctions की तरह करते हैं; इनको हम compound conjunctions कहते हैं.

even if
so that
on condition that
as well as
as soon as

Classification by Usage उपयोग पर आधारित वर्गिकरण
Based on the usage of the conjunction, conjunctions can be arranged into 2 classes.
Conjunctions को दो भागों में विभाजित किया जाता है

Co-ordinating Conjunctions
The conjunctions are called co-ordinating conjunction if the are connecting to independent words or group of words.
जब दो स्वतंत्र शब्दों या शब्द-समूहों जो जोड़ा जाता है तब जोड़ने वाले conjunction को co-ordinating conjunction कहते हैं.

Subordinating Conjunctions

When the two words or group of words being connected by the conjunction are dependent on each other, then it is known as a subordinating conjunction.
जब जुड़ने वाले दोनों शब्द या शब्द-समूह एक-दूसरे पर निर्भर हों तब जोड़ने वाले conjunction को subordinating conjunction कहते हैं.

Preposition
of Conjunctions
Interjection