2.3. Categorising materials

Categorising materials

Opening Speaking Exercise 4 on page 16

Collaborating Reading

Exercise c on page 16 on Wordwall:

https://wordwall.net/es/resource/110107856

Written Exercise 5b on page 16

Understanding Material Description Terminology in Engineering

Introduction

In engineering—especially in materials science, manufacturing, and design—precise language is essential. Small differences in wording can change the meaning of a technical description, particularly when explaining composition versus material origin. Terms like “comprise,” “consist of,” “made of,” “made from,” and “made out of” are often used interchangeably in casual conversation, but in engineering contexts they convey distinct and important differences.

This guide clarifies how each term is used, focusing on whether you are describing:

• the components of a system, or
• the source and transformation of a material

🧩 1. “Comprise” vs “Consist of”

These describe what components make up a system or material.

✅ Comprise

• Means: to include / be made up of
• Structure: Whole comprises materials
• More formal/technical, common in specifications and academic writing

Engineering examples:

• “The alloy comprises aluminum, copper, and magnesium.”
• “The composite comprises a polymer matrix and carbon fibers.”

⚠️ Avoid in formal writing: “is comprised of”

✅ Consist of

• Means: to be composed of
• Structure: Whole consists of parts
• Slightly less formal but widely accepted

Examples:

• “The circuit consists of resistors, capacitors, and an inductor.”
• “The material consists of two phases.”

👉 Key point: Both terms are very similar, but “comprises” is generally preferred in formal engineering documentation.

🔬 2. “Made of” vs “Made from” vs “Made out of”

These describe how a material or object originates, especially whether its original form is still recognizable.

✅ Made of → Original material is still identifiable

• The material’s identity remains largely unchanged

Engineering examples:

• “The beam is made of steel.”
• “The gasket is made of rubber.”
• “The housing is made of aluminum.”

👉 Use when the material is used directly without transformation

🔥 Made from → Material is transformed

• The original material is chemically or physically altered

Engineering examples:

• “Glass is made from silica.”
• “Polyethylene is made from ethylene.”
• “Paper is made from wood pulp.”

👉 Use when the original material is no longer recognizable

🔧 Made out of → Reconstructed or repurposed materials

• Emphasizes assembly or creative use of available materials
• Often used for prototypes or informal constructions

Examples:

• “The prototype was made out of scrap metal.”
• “The enclosure was made out of recycled plastic panels.”

👉 Less formal; rarely used in academic or formal engineering writing

⚖️ Quick Comparison Table

Phrase	Focus	Transformation	Formality	Example
Comprise	Components of a whole	No	High	“Alloy comprises Cu and Zn”
Consist of	Components of a whole	No	Medium	“System consists of sensors”
Made of	Material identity retained	No	High	“Rod made of steel”
Made from	Material transformed	Yes	High	“Plastic made from petroleum”
Made out of	Assembly / repurposing	Maybe	Low–Medium	“Frame made out of scrap”

🧠 Engineering Rule of Thumb

• Composition (parts) → comprise / consist of
• Material origin (substance) → made of / made from / made out of

✅ Practical Tip for Technical Writing

• Use “comprises” in formal reports and papers
• Use “made of” for solid, directly used materials
• Use “made from” for processed or transformed materials
• Avoid “made out of” in formal engineering contexts unless describing prototypes or informal builds

Collaborative Online Exercise: https://wordwall.net/es/resource/110131473