IELTS Vocabulary for Diagrams: Describing Processes and Flows

Quick Answer: To describe diagrams in IELTS Task 1 Academic Writing, you need precise vocabulary for sequencing (e.g., "firstly," "subsequently"), process verbs (e.g., "is heated," "is transformed"), and nouns for stages (e.g., "input," "output," "step"). This guide provides a comprehensive list of essential terms, sample answers for Band 7, 8, and 9, and common mistakes to avoid.

Table of Contents

Why Vocabulary Matters for Diagrams

Essential Vocabulary Categories

Sequencing Words and Phrases

Process Verbs for Active and Passive Voice

Describing Changes and Transformations

Nouns for Stages and Components

Band Score Comparison Table

Why Vocabulary Matters for Diagrams

In IELTS Academic Writing Task 1, you may be asked to describe a diagram showing a process or flow—such as how cement is made, how a water cycle works, or how a product is manufactured. Unlike graphs or charts, diagrams require you to explain the sequence of steps, the transformation of materials, and the relationships between components. Using precise, varied vocabulary is essential for achieving a high band score. Examiners look for:

Lexical resource: Use of a wide range of vocabulary, including less common words.

Grammatical range: Accurate use of passive voice, conditionals, and complex structures.

Coherence: Logical sequencing and clear transitions.

This post will give you the exact words and phrases you need to describe any process or flow effectively.

Essential Vocabulary Categories

To describe a diagram, you need four main types of vocabulary:

Sequencing words – to show the order of steps.

Process verbs – to describe actions (often in passive voice).

Nouns for stages and components – to name parts of the process.

Phrases for changes and transformations – to show how something evolves.

Let’s break these down.

Sequencing Words and Phrases

Sequencing is critical because you must show the logical flow of the process. Use a mix of simple and sophisticated words.

Simple	Sophisticated
First, then, next, after that	Initially, subsequently, thereafter, following this
Finally	Ultimately, in the final stage, at the end of the process

Example:

Simple: "First, the raw materials are collected. Then, they are crushed."

Sophisticated: "Initially, the raw materials are collected. Subsequently, they are crushed."

Pro tip: Avoid using "firstly" and "secondly" repeatedly. Instead, vary with phrases like "at the beginning," "once this is complete," or "after this step."

Process Verbs for Active and Passive Voice

Diagrams often describe industrial or natural processes where the action is done to the material. Use passive voice for objectivity.

Common process verbs:

Collect, gather, extract (for obtaining raw materials)

Crush, grind, chop (for breaking down)

Heat, cool, freeze (for temperature changes)

Mix, combine, blend (for combining elements)

Transform, convert, change (for major changes)

Produce, create, generate (for output)

Examples:

"The limestone is extracted from the quarry."

"The mixture is heated to a high temperature."

"The water is converted into steam."

For active voice (less common but useful for natural processes):

"The sun heats the water."

"The plant absorbs carbon dioxide."

Describing Changes and Transformations

Use these phrases to show how materials change:

Change of state: "The solid is melted into liquid." / "The liquid evaporates into gas."

Change of form: "The raw material is transformed into a finished product."

Change of size: "The particles are reduced in size."

Change of location: "The mixture is transferred to a container."

Advanced phrases:

"Undergoes a transformation"

"Is subjected to heat"

"Is broken down into"

"Is combined with"

Nouns for Stages and Components

Use precise nouns to name parts of the process:

General	Specific
Stage, step, phase	Initial stage, intermediate stage, final stage
Input, output	Raw material, finished product, by-product
Component, element	Ingredient, constituent, compound
Machine, device	Crusher, conveyor belt, furnace, reactor

Example:

"In the initial stage, the raw materials are fed into the crusher."

"The output of the first step is a coarse powder."

Band Score Comparison Table

Band	What Examiner Wants
6	Basic sequencing (first, then, finally); repetitive vocabulary; some passive voice errors.
7	Good range of sequencing words; uses passive voice correctly; some less common vocabulary (e.g., subsequently, undergoes).
8	Wide range of sophisticated vocabulary; accurate use of complex structures; clear logical flow; uses synonyms to avoid repetition.
9	Natural, precise vocabulary; flawless grammar; seamless transitions; demonstrates full control of lexical resource.

Sample Answers

Band 7: "The diagram shows how cement is produced. First, limestone and clay are collected. Then, they are crushed into a powder. Next, the powder is mixed and heated in a rotating kiln. After that, the mixture is ground again to produce cement. Finally, the cement is packed into bags." Band 8: "The illustration depicts the process of cement manufacturing. Initially, limestone and clay are extracted from the earth and subsequently crushed into a fine powder. This powder is then blended together and fed into a rotating kiln, where it is heated to an extremely high temperature. Following this, the resulting clinker is ground into a fine powder, which is the final product. Ultimately, the cement is packaged for distribution." Band 9: "The diagram delineates the multi-stage process of cement production. The process commences with the extraction of limestone and clay, which are subsequently conveyed to a crusher where they are reduced to a coarse powder. This powder is then thoroughly mixed and subjected to intense heat in a rotating kiln, causing a chemical transformation into clinker. Once cooled, the clinker is ground into a fine, homogeneous powder. In the final stage, the cement is meticulously packaged into bags, ready for transportation. This entire sequence involves both mechanical and thermal processes, ensuring the material undergoes a complete metamorphosis from raw mineral to finished product."

Common Mistakes

❌Using active voice for industrial processes: "The machine crushes the limestone" is less formal than "The limestone is crushed." Use passive voice to sound objective.

❌Repetitive sequencing words: Saying "first, then, then, then" is boring. Use "subsequently," "thereafter," "following this," "once this is complete."

❌Forgetting to describe the overall process: Always include an overview sentence (e.g., "Overall, the process consists of six main stages, beginning with extraction and ending with packaging."). This is essential for Task Achievement.

Top Tips

💡 Always write an overview: In the second paragraph, summarise the number of stages and the start/end points. This immediately shows the examiner you understand the diagram.

💡 Use a mix of active and passive: For natural processes (e.g., water cycle), active voice is fine. For man-made processes, prefer passive. Example: "Water evaporates from the ocean" (active) vs. "The limestone is crushed" (passive).

💡 Learn 5-6 sophisticated verbs: Words like "undergo," "subject to," "transform," "extract," "convey," and "grind" can elevate your score. Practice using them in sentences.

Resources

Check out IELTS Active for practice tests and study materials. You can also find diagram examples in official Cambridge IELTS books (e.g., Test 1, Task 1 in Cambridge 15).

FAQ

Q: Should I use active or passive voice for diagrams? A: For man-made processes, use passive voice (e.g., "the material is heated"). For natural processes (e.g., water cycle, life cycle), active voice is more common (e.g., "the sun heats the water"). Q: How many words should I write for a diagram description? A: Aim for 150–180 words. This is the minimum for Task 1, but going slightly over is fine if you cover all stages. Q: Can I use "it" or "they" to refer to the material? A: Yes, but be clear. If you say "it is then heated," make sure the previous sentence clearly states what "it" refers to. Q: What if I don't know the technical name of a machine? A: Use general terms like "device," "machine," "container," or "apparatus." For example: "The material is placed in a large container where it is heated." Q: Do I need to describe every single step? A: Yes, but you can group similar steps. For example: "The mixture is crushed and ground" instead of two separate sentences.

Key Takeaways

✅Use passive voice for industrial processes; active for natural ones.

✅Vary sequencing words (initially, subsequently, ultimately).

✅Include an overview sentence summarizing the process.

✅Learn 5-6 sophisticated verbs (extract, transform, undergo, convey, grind).

✅Avoid repetition by using synonyms for "step" (stage, phase, stage).

Related Posts:

IELTS Academic Writing Task 1: How to Describe a Process Diagram

Top 50 IELTS Vocabulary Words for Graphs and Charts

Common Mistakes in IELTS Writing Task 1 and How to Fix Them