substitute article; back-up
alternative means (alternate); alternative method
substitute device; replacement aircraft
non-substitutable; irreplaceable; unique; non-fungible
meat substitute; meat analogue; fake meat
alt text; fallback text; image description text
compensatory holiday (for working on a day off)
alternate reality game; ARG
pension replacement rate; income substitution rate (of the public pension)
alternate track; alternative track
alternate path; alternative path
CFC substitute; alternative CFCs; alternative chlorofluorocarbon
alternative plan; alternate proposal; counterplan; counterproposal