Why vocabulary accuracy matters
Lexical Resource is 25% of your Task 1 score. The examiner is not counting how many "advanced" words you use — they are checking whether your vocabulary is precise. A student who writes "rose steadily" for a gradual increase and "surged" for a sharp one demonstrates more lexical control than a student who writes "increased significantly" for every upward line.
Below are the eight shapes you will encounter in IELTS line graphs. Each one comes with a visual guide, a set of accurate words, and an example sentence showing how to use them in a report.
The shapes and their words
Common vocabulary mistakes
These are real mistakes from student reports. In each case, the problem is not grammar — it is choosing a word that does not match the size or speed of the change.
"Emissions plummeted from 11 to 9 metric tonnes over 30 years."
"Emissions declined gradually from 11 to 9 metric tonnes over 30 years."
"Plummeted" means a sudden, dramatic drop. A 2-unit decrease over 30 years is the opposite of sudden. The examiner notices this immediately — it signals that the student is using memorised vocabulary rather than reading the data.
"The figure edged up from 1.5 to 5.5 metric tonnes."
"The figure rose significantly from 1.5 to 5.5 metric tonnes."
"Edged up" means a very small increase. Nearly quadrupling is not small. Match the word to the scale of the change — not to how impressive you want to sound.
"The number increased and then it increased more and then it increased again."
"The figure rose steadily before accelerating sharply in the final decade."
Repeating the same verb is a Lexical Resource penalty. It tells the examiner you only have one word for "went up." Use different words for different phases of the same trend.
Tense — follow the data, not a rule
There is no single correct tense for line graphs. The tense follows what the data is showing. A student who shifts tense naturally when the data requires it signals genuine grammatical control.
Read the graph dates before you write. If the data runs into the future, switch tense at the point the projection begins. Consistency within each time period matters more than finding one "correct" tense.
Students ask me about tense rules more than anything else in Task 1. Here is the truth: if the graph shows 1990 to 2010 and you are writing in 2026, past simple is perfectly fine for the entire report. Do not overthink this. Pick a tense that fits the data and stay consistent. The examiner will not penalise you for using past simple on a historical graph.