What Are Compound Nouns?

A compound noun is a noun made from two or more words. These words join together to form a new word with its own unique meaning. The new meaning is often different from the individual words.

Compound nouns can be formed in many ways. They can combine different parts of speech, but they always function as a single noun.

• Noun + Noun: This is the most common type. For example, tooth + brush = toothbrush.
• Adjective + Noun: For example, black + board = blackboard.
• Verb + Noun: For example, wash + machine = washing machine.
• Noun + Verb: For example, sun + rise = sunrise.
• Preposition + Noun: For example, under + pass = underpass.

How Are Compound Nouns Written?

Compound nouns can be written in three main ways. Sometimes, the spelling can change over time, so it's good to check a dictionary if you are unsure.

• Closed form (one word): The two words are joined together without a space or hyphen. Examples: bedroom, sunflower, football.
• Hyphenated form (with a hyphen): The two words are connected by a hyphen. Examples: mother-in-law, passer-by, check-out.
• Open form (two separate words): The two words are written with a space between them, but they still act as a single noun. Examples: bus stop, post office, ice cream.

There are no simple rules to know which form to use. Often, new compound nouns start as two words, then become hyphenated, and finally become one word over time.

How Do We Pronounce Compound Nouns? (Stress Rules)

Pronunciation is very important for compound nouns, especially the stress. In most compound nouns, we stress the first word.

• TEAcup (not teaCUP)
• RAINbow (not rainBOW)
• FOOTball (not footBALL)

This stress pattern helps listeners understand that you are using a compound noun, which has a single, specific meaning.

Compound Nouns vs. Adjective + Noun Phrases: What's the Difference?

It can be confusing to tell the difference between a compound noun and an adjective describing a noun. The key differences are meaning and stress.

• Compound Noun: It is a single concept or item. The stress is usually on the first word. 例えば、, a GREENhouse is a building made of glass for growing plants.
• Adjective + Noun Phrase: The adjective describes a quality of the noun. The stress is usually on the second word. 例えば、, a green HOUSE is a house that is painted green.

Consider these examples:

• a BLACKbird (a type of bird) vs. a black BIRD (any bird that is black in color).
• a HOTdog (a type of food) vs. a hot DOG (a dog that feels warm).

The stress helps you communicate the correct meaning.

例

• My favorite ice cream flavor is vanilla.
• The traffic light turned red, so we stopped.
• She bought a new toothbrush this morning.
• We waited at the bus stop for twenty minutes.
• His mother-in-law is visiting next week.
• The children are playing football in the park.
• I need to go to the post office to send a letter.

練習

スペイン語話者がよく犯す間違い

Spanish speakers often make a few common mistakes with compound nouns:

• Using 'de' instead of combining nouns: In Spanish, you might say casa de pájaros. In English, we combine the nouns directly: birdhouse. Incorrect: house of birds. Correct: birdhouse.
• Incorrect word order: Spanish often places the adjective after the noun. With compound nouns, the modifying noun (like an adjective) comes first. Incorrect: board black. Correct: blackboard.
• Confusing compound nouns with adjective + noun phrases: Remember the stress rule! If you say green HOUSE, it means the color of the house. If you say GREENhouse, it means a specific building for plants.
• Forgetting that compound nouns are a single concept: Even if written as two words (e.g., bus stop), think of it as one item or idea.

よくある質問

What is a compound noun?

A compound noun is a noun made from two or more words that together form a single concept or item, like sunflower または bus stop.

Are all compound nouns written as one word?

No, compound nouns can be written in three ways: as one word (e.g., toothbrush), with a hyphen (e.g., mother-in-law), or as two separate words (e.g., ice cream).

How do I know if it's a compound noun or an adjective + noun?

Listen to the stress! For most compound nouns, the stress is on the first word （例：, GREENhouse). For an adjective + noun phrase, the stress is usually on the second word （例：, green HOUSE).

Why are compound nouns important for B1 English learners?

Learning compound nouns helps you expand your vocabulary, understand native speakers better, and express yourself more naturally. They are very common in everyday English conversations and texts.

関連レッスン

• Compound nouns