| (Expression OR)

Use the | when either one expression or another will do.

For example:

Both the expressions '(stabilised|stabilized) condition' and 'stabili(z|s)ed condition' will match 'stabilised condition' and 'stabilized condition'.

'(1|2|3) (person|people)' will match '1 person' and '2 people' and '3 people' but will not match '4 people' (it will also match '2 person' etc.). Note: this expression could have also been expressed using a character list.