twin

2. one of two similar things that make a pair
• The plate was one of a pair but I broke its twin.
Word Origin:
late Old English twinn ‘double’, from twi- ‘two’; related to Old Norse tvinnr. Current verb senses date from late Middle English.
Collocations:
Children
Having a baby/child
want a baby/a child/kids
start a family
conceive/be expecting/be going to have a baby/child
miss your period
become/get/ be/find out that you are pregnant
have a baby/a child/kids/a son/a daughter/twins/a family
have a normal/a difficult/an unwanted pregnancy; an easy/a difficult/a home birth
be in/go into/induce labour (especially US) labor
have/suffer/cause a miscarriage
give birth to a child/baby/daughter/son/twins
Parenting
bring up/ (especially NAmE) raise a child/family
care for/ (especially BrE) look after a baby/child/kid
change (BrE) a nappy/(NAmE) a diaper/a baby
feed/breastfeed/bottle-feed a baby
be entitled to/go on maternity/paternity leave
go back/return to work after maternity leave
need/find/get a babysitter/good quality affordable childcare
balance/combine work and childcare/child-rearing/family life
educate/teach/home-school a child/kid
punish/discipline/spoil a child/kid
adopt a baby/child/kid
offer a baby for/put a baby up for adoption
(especially BrE) foster a child/kid
be placed with/be raised by foster parents
Example Bank:
• His long-lost twin was searching for him.
• I was the older twin.
• My sister had twins.
• She had twin girls.
• The twins were separated at birth.
• a pair of identical twins
• adult twins who were raised apart
• an operation to separate conjoined twins

• the plot device of giving a character an evil twin

Cambridge Advanced Learner's Dictionary

twin / twɪn / noun [ C ]

B1 either of two children born to the same mother on the same occasion:

My sister has twin sons.

a twin sister

one of two very similar things:

The two countries are often regarded as economic twins.

Collins Advanced Learner’s English Dictionary

twin

[twɪ̱n]

twins, twinning, twinned
1) N-COUNT: oft N n If two people are twins, they have the same mother and were born on the same day.
  Sarah was looking after the twins...
  I think there are many positive aspects to being a twin...
  She had a twin brother and a younger brother.
2) ADJ: ADJ n Twin is used to describe a pair of things that look the same and are close together.
  ...the twin spires of the cathedral.
  ...the world's largest twin-engined aircraft.
3) ADJ: ADJ n Twin is used to describe two things or ideas that are similar or connected in some way.
  ...the twin concepts of liberty and equality...
  Nothing was done to save these women from the twin evils of begging or the workhouse.
4) VERB: usu passive When a place or organization in one country is twinned with a place or organization in another country, a special relationship is formally established between them. [BRIT]
  [be V-ed with n] Five Polish banks are to be twinned with counterparts in Western Europe...
  [V-ed] The borough is twinned with Kasel in Germany.
  Derived words:
  twinning N-UNCOUNT The twinning of Leeds and St Mary was formalised at a function held last week.
5) ADJ: ADJ n Twin towns or cities are twinned with each other. [BRIT]
  This led Zagreb's twin town, Mainz, to donate ₤70,000-worth of high-quality equipment.(in AM, use sister cities)
6) → See also identical twin, Siamese twin

Merriam-Webster's Advanced Learner's Dictionary

twin

³twin verb twins; twinned; twin·ning [+ obj]
1 : to bring (two things) together in close association - usually used as (be) twinned
• Research is twinned [=coupled] with technology.
• They will be twinned [=paired] in the pages of history.
• two cultures with a twinned destiny
2 Brit : to form a relationship between (two towns in two countries) - usually used as (be) twinned
• Our town is twinned with a town of roughly the same size in France.