single

5. only before noun (BrE) (also one-way NAmE, BrE) a single ticket, etc. can be used for travelling to a place but not back again
• a single ticket
• How much is the single fare to Glasgow?
compare return _n.(⁷)
see (in) Indian/single file at file _n., at a (single) glance at glance _n.
Word Origin:
Middle English: via Old French from Latin singulus, related to simplus ‘simple’.
Thesaurus:
single adj.
1. only before noun
• What is the single most important factor here?
individual • • particular • • specific • • separate • • distinct •
a/an single/individual/particular/specific/separate/distinct category/region
a single/particular/specific/separate event/incident/occasion
a single/particular/specific/distinct objective/purpose
2.
• The apartments are ideal for single people living alone.
unmarried • • divorced • • widowed • • separated • |especially BrE, especially written lone •
Opp: married
a single/unmarried/divorced/widowed/separated/lone man/woman/parent/mother/father
Example Bank:
• Marriage breakdown is common and there are a large number of single-parent families.
• Unemployment is the single most important factor in the rising crime rates.
• We eat rice every single day.

Derived: single somebody out

Cambridge Advanced Learner's Dictionary

single / ˈsɪŋ.ɡl̩ / adjective (NOT MARRIED)

A2 not married, or not having a romantic relationship with someone:

a single woman/man/person

He's been single for so long now, I don't think he'll ever marry.

The number of single-parent families dependent on the state has risen enormously in recent years.

single / ˈsɪŋ.ɡl̩ / adjective [ before noun ] (ONE)

B2 one only:

He knocked his opponent down with a single blow.

Not a single person offered to help her.

You haven't been listening to a single word I've been saying.

→ Compare double adjective

single / ˈsɪŋ.ɡl̩ / adjective [ before noun ] (SEPARATE)

B1 considered on its own and separate from other things:

Patience is the single most important quality needed for this job.

She lost every single thing when her house burned down.

Collins Advanced Learner’s English Dictionary

single

[sɪ̱ŋg(ə)l]

singles, singling, singled
1) ADJ: ADJ n (emphasis) You use single to emphasize that you are referring to one thing, and no more than one thing.
  A single shot rang out...
  Over six hundred people were wounded in a single day...
  She hadn't uttered a single word.
2) ADJ: det ADJ (emphasis) You use single to indicate that you are considering something on its own and separately from other things like it.
  Every single house in town had been damaged...
  The Middle East is the world's single most important source of oil.
3) ADJ Someone who is single is not married. You can also use single to describe someone who does not have a girlfriend or boyfriend.
  Is it difficult being a single mother?...
  I now have to face the rest of my life as a single person...
  Gay men are now eligible to become foster parents whether they are single or have partners.
4) ADJ: usu ADJ n A single room is a room intended for one person to stay or live in.
  A single room at the Astir Hotel costs ₤56 a night.
N-COUNT
Single is also a noun. It's ₤65 for a single, ₤98 for a double and ₤120 for an entire suite.
5) ADJ: ADJ n A single bed is wide enough for one person to sleep in.
6) ADJ: usu ADJ n A single ticket is a ticket for a journey from one place to another but not back again. [BRIT]
  The price of a single ticket is thirty-nine pounds.
  Ant:
  return
N-COUNT
Single is also a noun. ...a Club Class single to Los Angeles. (in AM, use one-way)
7) N-COUNT A single is a small record which has one short song on each side. You can also refer to the main song on a small record as a single.
  Kids today don't buy singles...
  The collection includes all the band's British and American hit singles.
8) N-UNCOUNT Singles is a game of tennis or badminton in which one player plays another. The plural singles can be used to refer to one or more of these matches.
  Boris Becker of West Germany won the men's singles...
  She is equally at home on the singles or doubles court.
  Ant:
  doubles
9) N-COUNT In cricket, a single is a hit from which one run is scored. In baseball, a single is a hit by which a batter reaches first base.
10) → See also single-
in single file → see file
  Phrasal Verbs:
  - single out

Merriam-Webster's Advanced Learner's Dictionary

¹sin·gle /ˈsɪŋgəl/ adj
1 always used before a noun : not having or including another : only one
• They lost by a single point. [=they lost by one point]
• A single shoe was found.
• It costs $10 for a single glass of wine!
• a single serving of carrots
• He earns $2,000 in a single week.
• There is a single [=uniform] standard for men and women.
- sometimes used to emphasize the largeness or importance of something
• The fingerprint turned out to be the single most important piece of evidence.
• Tobacco is the single greatest/largest/biggest industry in the state.
• Drunk driving is the greatest/largest/biggest single killer of high school students.
- sometimes used in negative statements to emphasize that there is a complete lack of something
• Not a single cookie was left.
• Not a single sound was heard.
• I could not hear a single word of what he said.
• We didn't get a single reply.
2 : not married or not having a serious romantic relationship with someone
• a club for single [=unattached, unmarried] people
• Are you single?
• a single parent/mother/father [=a mother or father who takes care of a child alone]
3
- used for emphasis after words like any, each, every, etc.
• He has more home runs than any other single player. [=than any other player]
• These laws apply to each single citizen.
• I drink milk every single day.
• She can't watch him every single minute.
4 always used before a noun : made for one person to use
• I stayed in a single room.
• I slept in a single bed. [=(US) twin bed]
5 Brit : one-way
• a single ticket
• How much is the single fare?