1. Once a fortnight.

Nuttall's Standard dictionary of the English language By Nuttall, P.Austin

• forthnightly,
• fortnighlt,
• fortnighlty,
• fortnighly,
• fornightly,
• fortrightly,
• dortnightly,
• cortnightly,
• vortnightly,
• gortnightly,
• tortnightly,
• rortnightly,
• firtnightly,
• fkrtnightly,
• flrtnightly,
• fortnightlty,
• fortnigtly,
• fortnightlyy,
• Fourtrightely,
• fortnightsly

• forty-ninth,
• fortnight.

The adjective form of the word "fortnightly" is "fortnightly".

The plural of the "fortnightly" can be the "fortnightlies".

The singular of the "fortnightly" can be the "fortnightly".