1. The quality of being active.

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

• activenss,
• inactiveness,
• activiness,
• activness,
• activetes,
• achiveness,
• zctiveness,
• sctiveness,
• wctiveness,
• qctiveness,
• axtiveness,
• avtiveness,
• aftiveness,
• adtiveness,
• activemess,
• activeneses,
• activenesse,
• plantiveness,
• amativenesss,
• antiqeness

• activated,
• actively,
• active voice,
• active site,
• active trust,
• activewear,
• activist,
• activism,
• active agent,
• activate,
• activase.

The adjective form of "activeness" is "active".

The plural of the "activeness" can be the "activenesses".

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