- (adjective) Having the colour of a clear sky or the deep sea.
- (adjective) Feeling sad or unhappy; low in spirits.
- (adjective, informal) Relating to indecent or offensive material.
- (noun) The colour blue.
- (noun) A genre of music originating in African-American communities in the southern United States.
- (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. See Cambridge Dictionary's full entry on “blue” for more examples.
Example Sentences
| Sentence | Level & 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
| Collocation | Part of speech | Example |
|---|---|---|
| bright blue | adjective + noun | She wore a bright blue jacket. |
| dark / deep blue | adjective + noun | The deep blue ocean stretched to the horizon. |
| pale / light blue | adjective + noun | The nursery walls were painted pale blue. |
| navy blue | adjective + noun | Navy blue suits are popular in offices. |
| sky blue | adjective + noun | The team plays in sky blue shirts. |
| feel / look blue | verb + adjective | You look blue — is everything all right? |
| out of the blue | idiomatic phrase | He called out of the blue after years of silence. |
| once in a blue moon | idiomatic phrase | We only argue once in a blue moon. |
| the blues | noun (plural) | She had a serious case of the Monday blues. |
| blueprint | compound noun | The 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
Synonyms
Explore More Vocabulary
Practise This Word
Want to understand the grammar behind this? Explore our Grammar guides.
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.