Adjective / Noun A2 — Elementary /bluː/

Blue — Definition, Examples & Pronunciation

The colour of the sky, a feeling of sadness, a genre of music — one small word with a rich variety of meanings.

Quick Definition
  1. (adjective) Having the colour of a clear sky or the deep sea.
  2. (adjective) Feeling sad or unhappy; low in spirits.
  3. (adjective, informal) Relating to indecent or offensive material.
  4. (noun) The colour blue.
  5. (noun) A genre of music originating in African-American communities in the southern United States.
  6. (noun, British) A sports award given at some British universities, especially Oxford and Cambridge.

What Does Blue Mean?

Blue is one of the most versatile words in English. Its primary meaning is the colour of a clear sky on a sunny day, but the word carries a remarkable range of extended and idiomatic senses that learners at every level need to know.

In everyday informal English, feel blue is a very common way to say you feel sad or slightly depressed — without the more serious connotations of clinical language. This emotional use probably dates to the 14th century and is firmly fixed in modern idiom: She felt blue after her best friend moved away.

As a noun, the blues (always plural when referring to the music) is a genre with deep roots in African-American history. The connection between blue, sadness, and this music is no accident: blues songs historically expressed hardship, longing, and resilience. Knowing this cultural context will help you read and listen to English at a much deeper level.

Etymology: From Old French bleu, derived from Frankish or Proto-Germanic *blao meaning “shining, bright”. The word entered Middle English in the 13th century, replacing the Old English hæwen. Cognates include Dutch blauw, German blau, and Swedish blå. The emotional sense “sad, melancholy” appears in English from at least the 14th century.

Example Sentences

SentenceLevel & usage note
The sky is bright blue today. A2 — basic colour adjective
She felt blue the first week abroad, but her English improved rapidly once she gained confidence. B1 — emotional adjective (set example)
He painted the front door a deep navy blue to match the shutters. B1 — colour shade as noun phrase
The invitation arrived completely out of the blue; nobody had expected the company to arrange a party. B2 — idiomatic phrase “out of the blue”
The documentary argued that Delta blues, far from being a purely regional phenomenon, had a transformative influence on twentieth-century popular music worldwide. C1 — blues as music genre, complex noun phrase

Collocations

CollocationPart of speechExample
bright blueadjective + nounShe wore a bright blue jacket.
dark / deep blueadjective + nounThe deep blue ocean stretched to the horizon.
pale / light blueadjective + nounThe nursery walls were painted pale blue.
navy blueadjective + nounNavy blue suits are popular in offices.
sky blueadjective + nounThe team plays in sky blue shirts.
feel / look blueverb + adjectiveYou look blue — is everything all right?
out of the blueidiomatic phraseHe called out of the blue after years of silence.
once in a blue moonidiomatic phraseWe only argue once in a blue moon.
the bluesnoun (plural)She had a serious case of the Monday blues.
blueprintcompound nounThe architect drew up a detailed blueprint for the extension.

Usage Notes

Colour shades: English has many fixed phrases for shades of blue. The most common are sky blue, navy blue, royal blue, baby blue, and powder blue. These are used as compound adjectives before a noun: a navy-blue tie, or as noun phrases: painted in baby blue.

Emotional use: Feel blue describes a mild, temporary sadness rather than serious depression. It is informal and conversational. Avoid it in formal academic writing; prefer despondent, melancholy, or low in spirits in more formal contexts.

The blues (music): When referring to the genre, blues always takes a plural verb with the definite article: the blues is / are — both forms occur, but the blues is treating it as an uncountable genre name is increasingly preferred in formal writing.

British university blue: In British English, get a blue / win a blue means to receive a sporting award from your university. This is a specialised usage mostly limited to Oxford, Cambridge, and a small number of other universities.

Common Mistakes

Watch Out For

I am feeling very blue today because I missed the exam.

I am feeling very low / sad today because I missed the exam. (Blue suggests mild wistfulness, not acute distress — do not overuse it for strong negative emotions.)

He told a blue story at the dinner — everybody laughed.

He told a blue joke at the dinner — everybody laughed. (Blue as “indecent” collocates with joke, humour, material — not story in this specific informal sense.)

Out of blue, she announced her resignation.

Out of the blue, she announced her resignation. (The idiom always requires the definite article: out of the blue.)

Related Words

bluebell blueprint bluebird blueberry blue-collar sky blue navy blue royal blue indigo azure cerulean cobalt

Synonyms

azure cobalt sapphire indigo cerulean sad (adj.) melancholy (adj.) downcast (adj.) dejected (adj.)

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Frequently Asked Questions about “blue”

What does blue mean in English?
Blue has several meanings in English. As an adjective it primarily describes the colour of the sky or sea ('a blue shirt'). It also means feeling sad or unhappy ('I'm feeling a bit blue today'). In informal contexts it can describe content that is indecent or offensive. As a noun, blue refers to the colour itself, a style of music, or a sports award at some British universities.
Is blue a noun or an adjective?
Blue can be both a noun and an adjective. As an adjective: 'She wore a blue dress.' As a noun: 'Blue is my favourite colour.' It can also function as a noun in the musical sense: 'She sings the blues.' In British university contexts, 'a blue' is a sports honour awarded to students who represent the university.
Why does blue mean sad?
The connection between blue and sadness dates back at least to the 14th century in English. One theory links it to the nautical practice of ships flying blue flags when a captain or officer had died. By the 16th century 'blue' was widely used to mean melancholy or low in spirits, and the expression 'feeling blue' is now a firmly established idiom in everyday English.
What is the difference between blue and the blues?
‘Blue’ (adjective) describes the colour or a feeling of sadness: 'She looked blue.' 'The blues' (plural noun) refers either to a state of depression — 'She has the Monday blues' — or to the genre of music that originated in the American Deep South: 'They went to see a blues band.' The musical term is almost always used with the definite article: 'the blues'.
What are common collocations with blue?
Common collocations include: bright blue, dark blue, pale blue, deep blue, sky blue, navy blue, royal blue, baby blue, powder blue, ice blue. Verbal collocations include: turn blue, go blue, paint something blue. Idiomatic phrases include: feel blue, once in a blue moon, out of the blue, blue-collar, blueprint, and blue-sky thinking.
What does ‘out of the blue’ mean?
'Out of the blue' is an idiom meaning suddenly and unexpectedly, with no warning. Example: 'She called me out of the blue after five years of silence.' The expression alludes to a bolt of lightning striking from a clear blue sky — something unexpected and surprising. It is very common in both spoken and written British English.
What does ‘once in a blue moon’ mean?
'Once in a blue moon' means very rarely or almost never. Example: 'I only eat fast food once in a blue moon.' A blue moon refers to the second full moon in a calendar month, which is a rare astronomical event. The idiom is informal and widely used in everyday British English.
What is the origin of the word blue?
Blue comes from Old French 'bleu', which derived from Frankish or Proto-Germanic 'blao', meaning 'shining' or 'bright'. It entered Middle English around the 13th century, replacing the earlier Old English word 'hæwen'. The same Germanic root gives related words in Dutch ('blauw'), German ('blau'), and Swedish ('blå').
What is a ‘blue’ in British universities?
At some British universities, particularly Oxford and Cambridge, a 'blue' is an award given to students who represent the university at the highest level in sport. At Oxford and Cambridge these are called a 'full blue' or 'half blue' depending on the sport. A student who has received this award is said to have 'won a blue' or 'got their blue'.
How can I practise using blue in English?
Try LexFizz's Flash Cards to review blue alongside related colour vocabulary, or use the Complete the Sentence exercise to practise blue in idiomatic phrases. Listening to blues music and reading song lyrics is also an engaging way to see the word used naturally in its emotional and cultural contexts.