Use 'seventieth' for highlighting major events like birthdays or anniversaries that mark 70 years. Grandma celebrated her seventieth birthday surrounded by family.
Pro Tip 2/3
Historical Context
'Seventieth' can reference historical or significant years, being 70 years after an event or start of an era. Next year, we will commemorate the seventieth anniversary of the peace treaty.
Pro Tip 3/3
Ordinal Usage
Emphasize 'seventieth' as an ordinal number indicating position in a sequence, not quantity. This novel is the seventieth in the series and continues the saga.