Apple ⬆️ lg (slight)⬇️ zte➡️↗️(slightly) The bar chart illustrates

2) Use vocabulary flexibly
You need to have a wide enough range of vocabulary that you can say the same thing in more than one way, that is, paraphrase. This is what the marking criteria mean by the phrase ‘allow some flexibility and precision’. You do this by using synonyms.
Paraphrasing also involves using different sentence structures, which I cover in the lesson on Grammar for Academic IELTS Task 1. 


3) Use collocations correctly
The marking criteria specifically mention the correct use of collocations as something you'll be assessed on.
A collocation is a combination of two or more words that sound correct to a native speaker when used together. The word combination often doesn’t work if you try to replace the first word with a synonym. For example, we say,

• 
  heavy rain but not weighty rain
  

• 
  fast food not quick food
  

• 
  keen interest not eager interest
  

My advice here is to only use collocations you are 100% sure are correct. These are something to focus on when learning vocabulary and I include some Task 1 related examples in the word lists we’ll now focus on.

Key Vocabulary for Academic IELTS Task 1

Adjective & Adverbs

In your IELTS Task 1 essay, you are required to describe what you see in a chart, graph, table, map or a diagram, most especially, to record changes in the data. To do this, you will use describing words, that is, adjectives and adverbs.

• 
  Adjectives are words that describe or modify nouns or pronouns.
  

• 
  Adverbs are words that describe or modify verbs or adjectives.
  

Adverbs can generally be formed by adding ‘ly’ to the end of the adjective.

Here is a table of adjectives and adverbs relevant to Task 1 questions. Don’t try to learn them all. This is only a very short essay (min. 150 words) so you won’t be able to include much detail.
Learn 2 or 3 words for large changes and 2 or 3 for small or moderate changes.