All 7 Uses of

coincidence
in
Murder On The Orient Express

Have we here a coincidence, or what?†
Chpt 1.7 *

coincidence = a situation where things happened at the same time by chance even though it was unlikely

"As, to that, the coincidence is not perhaps so great as it seems," said the doctor.†
Chpt 2.14

mon cher, that would be indeed stretching coincidence a little too far," said M. Bouc.†
Chpt 3.8

He went on slowly: "I was particularly struck by the extraordinary difficulty of proving a case against any one person on the train, and by the rather curious coincidence that in each case the testimony giving an alibi came from what I might describe as an 'unlikely' person.†
Chpt 3.9

For so many people connected with the Armstrong case to be travelling by the same train through coincidence was not only unlikely: it was impossible.†
Chpt 3.9

Definitions:

(1) (coincidence)
a situation where two things happened at the same time or in the same way by chance even though it was unlikely

(for example, if two students in the same class met by accident while visiting another country)
(2) (meaning too rare to warrant focus)
meaning too rare to warrant focus:

Much more rarely coincidence can refer to things coinciding (occurring or operating at the same place or time). For example:
- the coincidence of a target and cross hairs
- the coincidence of entangled particles in quantum physics