Explanation at your level:
The diameter is how wide a circle is. Imagine a circle. Draw a line from one side to the other. The line must go through the middle. That line is the diameter. It helps you know the size of round things like balls or plates. If you want to know how big a circle is, you measure the diameter.
When you look at a round object, the diameter is the distance across it. You must measure through the center point. It is different from the radius, which is only half of the distance. We use this word in math class and when we talk about the size of things like wheels or pipes.
In geometry, the diameter is a key measurement for circles and spheres. It is defined as a straight line passing through the center, connecting two points on the edge. You will often see this term in technical instructions, such as 'measure the diameter of the hole before drilling'. It is a very precise way to describe the width of circular objects.
The term diameter is frequently used in both academic and practical contexts. Beyond basic geometry, it is used in engineering and manufacturing to specify the dimensions of circular components. Understanding the relationship between the diameter and the circumference (the distance around the edge) is a fundamental skill in many technical fields. It is a stable, neutral term used whenever precision is required.
While primarily a geometric term, diameter is often employed in scientific discourse to describe the scale of spherical bodies, such as planets or cells. In a more abstract sense, it can denote the extent or scope of a circular area of effect. The precision of the word makes it indispensable in fields ranging from astronomy to mechanical engineering. Its usage is consistent across formal registers, emphasizing accuracy and clarity.
Etymologically derived from the Greek diametros, the word diameter encapsulates the ancient human pursuit of quantifying space. In advanced literary or technical writing, it serves as a precise anchor for spatial descriptions. Whether discussing the diameter of a subatomic particle or the metaphorical diameter of a social circle, the word retains its connotation of absolute measurement. It is a cornerstone of mathematical vocabulary, representing the intersection of logic and physical reality.
30秒でわかる単語
- Diameter is the width of a circle through the center.
- It is exactly twice the length of the radius.
- Used in math, science, and everyday DIY.
- Pronounced die-AM-e-ter.
Think of the diameter as the ultimate shortcut across a circle. If you were to walk straight through the middle of a circular park from one side to the other, the distance you travel is the diameter.
It is a fundamental concept in geometry. Without understanding the diameter, we wouldn't be able to easily figure out how much fence we need to go around a circular garden or how much paint is required for a round table.
Remember, the line must pass through the exact center. If it misses the center, it is just a chord, not a diameter. It is the widest possible distance you can measure across any round object, whether it is a coin, a planet, or a pizza.
The word diameter has a fascinating history rooted in ancient Greek. It comes from the Greek word diametros, which literally means 'measure across'.
The word is a combination of dia, meaning 'through', and metron, meaning 'measure'. It entered the English language in the 14th century via Old French. Mathematicians have used this term for thousands of years to describe the properties of circles.
It is a classic example of how scientific language often preserves ancient roots. When you use this word, you are connecting directly to the language used by early scholars who first mapped out the rules of geometry.
In everyday life, you will hear diameter used when discussing physical dimensions. You might hear it at a hardware store when buying pipes or in a kitchen when measuring the size of a pan.
It is commonly paired with adjectives like internal, external, or approximate. For example, 'The internal diameter of the tube is 5cm.' This is very common in technical or construction contexts.
While it is a precise mathematical term, it is perfectly acceptable in casual conversation. If you are describing the size of a giant tree trunk or a circular rug, using diameter is the most accurate way to be understood.
While diameter is a technical term, it appears in phrases describing distance or scope.
- Across the diameter: Used to describe a direct path through a circular space.
- Within a certain diameter: Used to define a circular area of influence or search.
- Diameter of influence: Used in physics to describe how far a force reaches.
- Expanding the diameter: Often used metaphorically for growing a project or scope.
- Measuring the diameter: A literal phrase often used in DIY or craft projects.
The word diameter is a countable noun. You can have one diameter or multiple diameters. It is typically used with the definite article 'the' when referring to a specific object.
Pronunciation: In the US, it is pronounced /daɪˈæmɪtər/. In the UK, it is similar but often with a slightly crisper 't'. The stress is on the second syllable: di-AM-e-ter.
It rhymes with words like thermometer, parameter, and barometer. Keeping the stress on the second syllable is the key to sounding natural when saying this word.
Fun Fact
The word has remained almost unchanged in meaning for over 2,000 years.
Pronunciation Guide
Sounds like die-AM-ih-ter
Sounds like die-AM-uh-ter
Common Errors
- Stressing the first syllable
- Mispronouncing the 't' as a 'd'
- Dropping the final 'r' sound
Rhymes With
Difficulty Rating
Easy to read
Easy to write
Easy to say
Easy to hear
What to Learn Next
Prerequisites
Learn Next
上級
Grammar to Know
Countable Nouns
One diameter, two diameters.
Definite Articles
The diameter of the circle.
Adjective Placement
A large diameter.
Examples by Level
The diameter of the circle is ten centimeters.
diameter = width
Use 'of' after diameter
Measure the diameter of the ball.
measure = check size
Imperative verb
This plate has a large diameter.
large = big
Adjective placement
What is the diameter of the coin?
coin = money
Question structure
The circle's diameter is small.
small = little
Possessive apostrophe
Draw a line for the diameter.
draw = make a picture
Prepositional phrase
The tree has a wide diameter.
wide = broad
Adjective usage
Find the diameter of the wheel.
wheel = round part of a car
Verb usage
The pipe has a diameter of two inches.
We need to know the diameter of the lid.
The sun has a very large diameter.
Can you measure the diameter of this pizza?
The diameter is twice the radius.
The hole has a small diameter.
Check the diameter before you buy the part.
The diameter is marked on the box.
The internal diameter of the tube is crucial for the flow rate.
Engineers calculated the diameter of the tunnel accurately.
The planet's diameter is roughly 12,000 kilometers.
We need a screw with a specific diameter.
The diameter of the circular base is 30cm.
She measured the diameter of the tree trunk with a tape.
The diameter of the wire is too thin for this current.
The diameter of the lens determines how much light enters.
The telescope allows us to observe the diameter of distant stars.
The manufacturer specifies an external diameter of 50mm.
The diameter of the crater was estimated to be five miles.
We are looking for a pipe with a larger diameter.
The diameter of the circle is the longest chord.
The project scope expanded in diameter to include more regions.
The diameter of the sphere is constant in all directions.
The diameter of the nozzle must be adjusted for pressure.
The microscopic diameter of the fiber makes it incredibly strong.
The diameter of the aperture can be adjusted for exposure.
The diameter of the orbit is affected by gravitational pull.
The diameter of the sphere influences the surface area to volume ratio.
The diameter of the cylinder is essential for calculating displacement.
In cross-section, the diameter reveals the internal structure.
The diameter of the storm eye was surprisingly small.
The diameter of the beam is critical for laser precision.
The diameter of the celestial body was measured using parallax.
The diameter of the vascular bundle is a key botanical feature.
The diameter of the aperture is inversely proportional to depth of field.
The diameter of the sphere of influence is growing rapidly.
The diameter of the vortex was captured in the simulation.
The diameter of the conduit is insufficient for the required flow.
The diameter of the circular path is defined by the radius of curvature.
The diameter of the domain is a central concept in topology.
反対語
よく使う組み合わせ
Idioms & Expressions
"within a certain diameter"
Inside a circular area.
Stay within a 5-mile diameter of the camp.
neutral"across the diameter"
Directly through the middle.
Draw a line across the diameter of the circle.
formal"diameter of influence"
The range of an effect.
The storm had a wide diameter of influence.
formal"full diameter"
The complete width.
The tree reached its full diameter after 20 years.
neutral"at the diameter"
At the widest point.
Measure it at the diameter.
neutral"equal to the diameter"
The same as the width.
The height is equal to the diameter.
formalEasily Confused
Both relate to circles.
Radius is half.
The radius is 5cm, so the diameter is 10cm.
Both relate to circles.
Circumference is the distance around.
The circumference is the perimeter of the circle.
Both are straight lines across.
Diagonal is for polygons.
The diagonal of the square is long.
Both mean how wide.
Width is general.
The width of the table is 1 meter.
Sentence Patterns
The diameter of [object] is [number].
The diameter of the pipe is 5cm.
Measure the diameter of the [object].
Measure the diameter of the wheel.
The diameter is equal to [value].
The diameter is equal to twice the radius.
We need a [adjective] diameter.
We need a larger diameter.
The diameter is determined by [factor].
The diameter is determined by the pressure.
語族
Nouns
Adjectives
関連
How to Use It
7
Formality Scale
よくある間違い
Radius goes from center to edge; diameter goes edge to edge.
They are distinct geometric measurements.
Diameter is specific to circles/spheres.
Stress is on the second syllable.
It is a specific measurement, so it needs an article.
Tips
Memory Palace Trick
Visualize a giant 'D' stretching across a circle.
When Native Speakers Use It
Whenever they need to describe the width of something round.
Cultural Insight
It is a standard term in all English-speaking school systems.
Grammar Shortcut
Always use 'the' before diameter when it is specific.
Say It Right
Focus on the 'AM' sound in the middle.
Don't Make This Mistake
Don't confuse it with radius!
Did You Know?
The word is over 600 years old in English.
Study Smart
Draw circles and label the diameter and radius.
Rhyme Time
Rhyme it with thermometer to remember the stress.
Context Matters
Use 'internal diameter' for hollow objects.
Memorize It
Mnemonic
Di-AM-eter: The line goes through the AM (middle) of the circle.
Visual Association
A pizza cut exactly in half through the center.
Word Web
チャレンジ
Measure the diameter of three round objects in your room.
語源
Greek
Original meaning: measure across
文化的な背景
None.
Commonly used in school math and DIY projects.
Practice in Real Life
Real-World Contexts
At school
- Calculate the diameter
- Draw the diameter
- Find the diameter
At work
- Check the diameter
- Specify the diameter
- Measure the diameter
Shopping
- What is the diameter?
- Need a larger diameter
- Check the diameter size
Science
- Diameter of the planet
- Diameter of the cell
- Diameter of the orbit
Conversation Starters
"How do you measure the diameter of a tree?"
"Why is the diameter important in construction?"
"Can you explain the difference between radius and diameter?"
"What is the diameter of your dinner plate?"
"How would you find the diameter of a circle if you only had a string?"
Journal Prompts
Describe a time you had to measure something round.
Why do we need precise measurements like diameter?
Imagine a world without circles; how would we use the word diameter?
Explain the relationship between radius and diameter to a younger student.
よくある質問
8 問No, the diameter is twice the radius.
No, it must be a straight line.
Yes, that is the defining feature.
No, we use diagonal for squares.
Diameters.
It is neutral and used in both formal and informal contexts.
Yes, it works for any round object.
Think of it as di-AM-eter, like a drum beat.
自分をテスト
The ___ of the circle is 5cm.
Diameter is the correct term for a circle's width.
Which line is a diameter?
A diameter must pass through the center.
The diameter is twice the length of the radius.
The radius is from center to edge, so two radii make one diameter.
Word
意味
Matching terms to definitions.
The diameter is ten cm.
The ___ diameter of the tube is 2 inches.
Internal diameter is a standard technical term.
What does 'diametrically opposed' mean?
It refers to being at opposite ends of a diameter.
A diameter can be a chord.
A diameter is the longest possible chord.
Which word is an antonym of diameter in a geometric sense?
Radius is the most direct geometric counterpart.
The ___ of the circular orbit is 1 million miles.
Diameter is the correct term for the width of an orbit.
スコア： /10
Summary
The diameter is the straight-line distance across a circle, passing through the center.
- Diameter is the width of a circle through the center.
- It is exactly twice the length of the radius.
- Used in math, science, and everyday DIY.
- Pronounced die-AM-e-ter.
Memory Palace Trick
Visualize a giant 'D' stretching across a circle.
When Native Speakers Use It
Whenever they need to describe the width of something round.
Cultural Insight
It is a standard term in all English-speaking school systems.
Grammar Shortcut
Always use 'the' before diameter when it is specific.
例文
The diameter of this large pizza is 12 inches.
Related Content
文脈で学ぶ
この単語を他の言語で
scienceの関連語
acid
A1これは、酸っぱい味がして、物を溶かすこともある化学物質のことだよ。科学では、pHが7より小さい液体を指すんだ。
algebra
A1数式のなかの分からない数を、文字や記号を使って表す数学の一分野だよ。計算ルールを使って答えを導き出すんだ。
atom
A1An atom is the smallest possible part of a chemical element. Everything in the world is made of millions of these very tiny particles.
atomic
A1Atomic relates to the very small parts called atoms that make up everything in the world. It is often used to describe science, energy, or very small things.
calculus
A1Calculus is a high-level branch of mathematics that studies how things change. It uses special symbols to calculate things like the speed of an object or the area of a shape.
catalyst
A1A catalyst is something that makes a change happen faster or more easily. In science, it is a substance that speeds up a chemical reaction without being changed itself.
circuit
A1回路（かいろ）は、電気が流れる完全な道のことです。電気の通り道全体を指します。
circumference
A1The circumference is the distance around the outside edge of a circle or a round object. It is a measurement that tells you how long the boundary of a round shape is.
constant
A1A constant is something that stays the same and does not change. In science and math, it is a fixed number or a part of an experiment that is kept the same while other things vary.
decimal
A1A decimal is a number that uses a dot to show parts of a whole. It is based on the number ten and helps show values smaller than one.
