1. That may be sustained.

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

• sastainable,
• sustianable,
• sestainable,
• sustainbale,
• sustaianable,
• substainnable,
• sustenable,
• sustaible,
• substainable,
• susatinable,
• susteinable,
• sustinable,
• sustainalbe,
• sustinale,
• sustanable,
• sustainabily,
• sustaniable,
• sustanably,
• sustanible,
• sustainale

• sustainer,
• sustainability,
• sustentation,
• sustenance,
• sustainment,
• sustained.

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

The plural form of the word "sustainable" is "sustainables".

The singular form of the word "sustainable" is "sustainability"