Imagine a PTE Academic Describe Image item with a line graph. Visitor numbers rise from 20,000 to 55,000 in two months, drop to 18,000, move up and down for a year, then stay near 30,000.
A weak response says:
"The number went up, then went down, then changed, and finally stayed the same."
The directions are mostly right. The shapes are missing. Was the rise small or forceful? Was the fall gradual or steep? Did the final value reach one high point, or did it remain broadly stable?
That is the lexical decision: name the size and shape of a change, not only its direction. Pearson's current guidance asks you to cover the image's main information and relationships. Precise trend verbs help when the image actually supports them.
The lexical decision: what shape do the data show?
Ask four questions before you choose a word:
- Is the movement large and fast, or modest and slow?
- Does it go in one direction, or repeatedly up and down?
- Has the movement stopped, or is it still weakening?
- Did the value rise after an earlier fall?
The answer separates words that learners often treat as interchangeable.
1. Surge vs. spike: strong rise or brief peak?
Surge describes a rapid, powerful rise in a measurable quantity.
"Demand surged from 20,000 to 55,000 units in two months."
As a verb, surge is intransitive: demand surged; a campaign did not surge demand. Use by for the amount of change and to for the final level: surged by 35,000 to 55,000.
Spike is especially useful for a sudden, brief peak that falls back quickly. A graph with one narrow jump and an immediate return shows a spike. A strong rise sustained across several points may be a surge.
Do not call every increase a surge. A rise from 50% to 52% across five years is more safely an increase or uptick. Surge makes a strong claim about speed and scale.
2. Plummet vs. decline: steep and rapid or neutral?
Plummet combines direction, scale, and speed: a value falls very steeply and rapidly.
"After its May high, attendance plummeted by more than half."
The changing quantity is the subject. Write attendance plummeted, not the closure plummeted attendance. Use from X to Y for endpoints and by X% for the size of the fall.
Decline is neutral and can describe a gradual fall. If a graph drifts down from 70 to 64 across six years, plummeted is an overclaim. A strong word is not automatically a precise word.
Avoid plummeted sharply in a short description. Plummet already contains that force.
3. Fluctuate vs. vary: movement over time or differences?
Fluctuate describes repeated or irregular movement up and down over time.
"Prices fluctuated between $40 and $55 during the second half of the year."
Use between A and B or from A to B for the bounds. The verb is normally intransitive: prices fluctuate.
Vary is broader. It can compare categories at one time: prices vary by region. That sentence does not say each region's price moved up and down. If one line repeatedly rises and falls across months, fluctuate is the clearer choice.
A one-way rise, one-way fall, or flat line does not fluctuate. The verb also says nothing by itself about the cause or the long-term direction.
Understanding is only the first step.
Lyra Practice helps you retrieve and use high-value workplace expressions in realistic situations until they feel natural.
Start a practice session →4. Plateau vs. level off: the same shape, different forms
Both plateau and level off can describe a trend that had been rising or falling and then stays broadly stable.
"Subscriptions plateaued at about 80,000."
"Subscriptions leveled off at about 80,000."
As verbs, they overlap. Do not invent a difference the graph does not show.
The useful distinction is grammatical: plateau can also be a countable noun.
"Subscriptions reached a plateau in June."
You cannot write reached a level off. Both verbs are intransitive in this trend sense. The line plateaus or levels off; the company does not plateau the line.
A plateau is a broadly stable phase, not one unchanged point. It is also neutral. Flat pollution levels may be disappointing; flat error rates after a steep fall may be welcome.
5. Taper off vs. level off: still falling or now stable?
Taper off means become gradually smaller, weaker, slower, or less frequent.
"After the launch, daily downloads tapered off over the next six weeks."
The decline is progressive. It may later reach zero, but the verb does not require that.
Level off means the earlier movement has stopped and the value now holds at a roughly steady level.
Compare:
"Calls tapered off from 900 to 500 per day."
"Calls then leveled off at roughly 500 per day."
The first line is still moving down. The second has stopped moving down. A graph can show both stages, so using both verbs is not repetition.
6. Rebound vs. rise: what happened before?
Rebound means rise or improve again after an earlier fall, loss, slump, or weak period.
"Revenue rebounded to $4 million after falling below $3 million in April."
The prior fall is part of the meaning. If the graph begins low and rises with no earlier decline shown or stated, call it a rise, not a rebound.
A rebound need not restore the old high. If a value falls from 100 to 40 and then rises to 65, it has rebounded even though it has not fully recovered.
You can use the matching noun: a rebound in revenue. In the verb frame, use rebounded from, rebounded to, or rebounded by with accurate numbers.
7. Trajectory: the path across several points
Trajectory describes the shape and direction of movement over time. It is not one change or one data point.
"Despite the monthly fluctuations, the long-term trajectory was downward."
This noun helps you separate local movement from the larger pattern. A line can fluctuate while following an upward trajectory. One strong month does not establish a trajectory.
Give the noun a useful modifier: upward, downward, flat, gradual, or unsustainable trajectory. Avoid empty claims such as a great trajectory. The image should show the pattern you name.
Weaker and more precise: the same graph
Suppose a chart shows app downloads at 10,000 in January, 38,000 in March, 12,000 in April, between 15,000 and 23,000 from May to August, and near 20,000 from September onward.
Weaker version:
"Downloads increased, decreased, changed for several months, and then stayed stable."
More precise version:
"Downloads surged from January to March before plummeting in April; they then fluctuated between 15,000 and 23,000 through August and finally leveled off at about 20,000."
The second version is better because each verb matches visible evidence:
- Surged fits the fast, large rise.
- Plummeting fits the steep fall.
- Fluctuated fits repeated movement in both directions.
- Leveled off fits a stable final phase.
The verbs do not explain why any change happened. A chart alone may show shape without showing cause.
A sample response
Prompt: a line chart compares library visits in three districts from 2020 to 2025.
"The chart compares library visits across three districts over five years. Central District followed an upward trajectory, with visits surging in 2022 before leveling off at about 90,000. East District fluctuated between 45,000 and 60,000, while West District plummeted in 2021 and then partially rebounded. Overall, Central ended with the highest attendance, whereas West never returned to its starting level."
This response names the main relationships and adds a conclusion grounded in the imagined figures. It does not list every point.
Common mistakes
- Using dramatic verbs for small movements. Surge and plummet need evidence of speed and scale.
- Using a transitive trend verb. Write sales surged, prices plummeted, and demand fluctuated.
- Mixing up by and to. Fell by 20% names the change; fell to 20% names the endpoint.
- Calling a peak a plateau. A peak is one highest point and may be followed by a fall; a plateau lasts.
- Calling a continuing decline a level-off. If the values keep falling gradually, they are tapering off.
- Calling any later rise a rebound. A rebound needs an earlier fall or weak period.
- Treating trajectory as one event. It requires a pattern across several points.
Quick check
1. A line rises from 40 to 95 in one month, stays above 90 for three months, then eases. Which word best captures the initial movement?
A. surged
B. fluctuated
C. leveled off
2. Values are 70, 61, 55, 52, and 50. Which phrase fits the continuing gradual fall?
A. rebounded
B. tapered off
C. reached a plateau
3. A metric falls from 100 to 40, then rises to 65. Which claim is accurate?
A. It fully recovered.
B. It rebounded but did not regain its earlier level.
C. It fluctuated because every change is a fluctuation.
Answers: 1-A, 2-B, 3-B. A surge is fast and large, tapering is a continuing gradual decline, and a rebound does not require full recovery.
Practice prompt
Sketch five values: 30, 65, 20, 35, 35. Give yourself 40 seconds. Describe the overall image and use two precise trend words. Then check whether each word matches the size, direction, and prior movement shown.
If you want to practice making these choices in fresh contexts, try Lyra Practice.
This independent guide is not affiliated with Pearson. Explore more at the PTE Academic Vocabulary Practice hub and the Exam English hub.
Sources
- PTE Academic Speaking & Writing test format — Pearson
- PTE Academic Describe Image test tips — Pearson
- PTE Academic Test Taker Score Guide — Pearson