isolation; segregation; separation; quarantine
barrier wall; bulkhead; partition; septum; diaphragm
isolation; separation; remoteness; seclusion; reclusion; inaccessibility
space; interval; space character; whitespace
reserve; reticence; unfriendliness; estrangement
every other week; every two weeks
every other day; every second day
separation of ages; being of a different age
every second month; every other month
biennially; every second year; every other year
reserve; alienation; estrangement
headway (between trains, etc.); frequency