Meaning: Linking words are the words used to link one piece (paragraph/idea/sentence/part of the sentence) of writing with another piece of writing. These are also known as linking devices, connectors or connecting devices. The concept of connectors can be understood by the following example:
Simple sentences:
Computers are increasingly used in today’s world. Computers can work with great speed and accuracy.
Complex sentence using linking words:
Computers are increasingly used in today’s world due to their great speed and accuracy.

Usage: The use of linking devices is highly appreciated in the IELTS Writing and Speaking. Although, a correct essay or a letter can be written even without using connectors, but, for the candidates aspiring 7 bands or above, the use of connectors is highly recommended.

Benefits: Linking devices act as a connection between two ideas and hence, they increase the readability and understandability of the text. There are many advantages of using linking words in Writing and Speaking.
–         Making additions
–         Comparison and contrast
–         Giving reasons
–         Consequences
–         Highlighting examples
–         Highlighting opinions
–         Highlighting conclusions

Making additions: These connectors can be used to add more ideas in continuation with the line of thought which is being discussed. In the IELTS essay writing, these connectors are very useful in connecting ideas within a single paragraph or to start another paragraph having line of thought.
For example: Computers are increasingly used in today’s world due to their great speed and accuracy. In addition, they are cost effective as they reduce the need of hiring new staff.
Other useful words:
Moreover
Furthermore
Additionally
In addition to
Also
And
As well as

Comparison and contrast: These are the linking words that are used to compare two ideas or viewpoints to clarify their differences. These are very useful in explaining the differences in the IELTS writing and speaking.
For example: Independent houses allow more privacy whereas apartments are affordable for more number of people.
Other useful words:
But
However
Besides
Regardless
Apart from this
Nevertheless
Nonetheless
Notwithstanding
In contrast
On the contrary
While
In comparison to
Whereas

Giving reasons: It is very crucial to give explanation of every point that is mentioned in the body paragraphs of the IELTS essays. This often includes giving reasons of whichever idea the writer mentions. These words help in making the reasons identifiable.
For example: Apartments are in high in demand in all the big cities of the world because they are easily affordable.
Other useful words:
As
Because
Due to

Consequences: These words help the writer in describing a situation or action or idea and its result. These words are very useful in analytical essays where consequences are required to be mentioned.
For example: Junk food is tasty, therefore, children prefer to eat it.
Other useful words:
Consequently
Hence
Therefore
Thus

Highlighting examples: It is advisable to give at least one example in an IELTS essay to make the arguments more understandable. These phrases can be used for giving examples.

As an instance, this sentence itself is an example.
Other useful words:
For example
To illustrate
As an instance
To exemplify
To quote an example

Highlighting opinions: In some of the IELTS essays, it is mandatory to give your opinion as the writer of the essay. Also, it is advisable to make it clear that it is the writer’s opinion. So, these words can be used to emphasize that the given viewpoint is the writer’s viewpoint.
For example: As per my perspective, public transport should not be free of cost.
Other useful words:
I think
I believe
In my opinion
According to me
As per my perspective
I opine

Highlighting conclusions: Conclusion is an essential component of every essay. This gives the ultimate crux of the entire essay. It is very important for the writer to emphasize the sentence from where conclusion starts.
For example: To conclude, the use of computers in education is a positive development due to its numerous benefits.
Other useful words:
To conclude
In conclusion