To get a high score in IELTS Task 1 writing of the academic IELTS you need to give accurate and strong description and analyses for the provided graph(s) or diagram. In this minimum 150 word essay it is easy to keep repeating words and numbers.

Lexical resources will determine 25% of your score in Task 1, you have to enrich your vocabulary to hit a high score.

To demonstrate that you have great lexical resources you need to:

Use correct synonyms in your writing.
Use a range of vocabulary.
Do not repeat words and phrases from the exam questoin unless there is no alternative.
Use less common vocabulary.
Do not use the same word more than once/twice.
Use precise and accurate words in a sentence.

Nouns:
a rise
an increase
a surge
a growth
a peak
a fluctuation
a variation
a period of stability
a plateau
a fall
a decrease
a decline
a dip

Verbs
to rise
to increase
to surge
to grow
to peak
to skyrocket
to fluctuate
to vary
to fall
to decrease
to decline
to dip
to dive
to plunge

Phrases
to show an upward trend
to show a downward trend
to hit the highest point
to hit the lowest point
to reach a peak
to show some fluctuation
to fluctuate wildly
to remain stable
to remain static
to remain unchanged
to stay constant
to reach a plateau
to level off
to flatten out
the highest
the lowest
the second highest
the third highest
compared to
compared with
relative to

Adverbs
sharply
suddenly
rapidly
abruptly
dramatically
significantly
steadily
considerably
markedly
slightly
gently
gradually
wildly

Adjectives
sharp
sudden
rapid
abrupt
dramatic
steep
significant
steady
considerable
marked
slight
gentle
gradual

Words for IELTS exam for writing task 1 practice: