1. A conjunction is a word used to join words, groups of word or sentence.
2. A conjunction can be co-ordinating when it is used to join two independent and subordinating when one of the statements is dependent on the other.

Apply and Learn:

Q1. He is more than eighty years old, _______ he is quite healthy (still/or)
Answer: still

Q2. Revise your lessons regularly, ________ you may forget them (therefore/otherwise)
Answer: otherwise

Q3. We stopped working _______ the clock struck five. (when/while)
Answer: when

Q4. The crops dried up ______ it did not rain at all. (because/if)
Answer: because

Q5. Do not switch off the lights _______ everybody has gone away. (still/until)
Answer: until