1. With increase of wealth.

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

• rainfull,
• painfullly,
• gainfull,
• baenfully,
• fainfully,
• vainfully,
• bainfully,
• hainfully,
• yainfully,
• tainfully,
• gzinfully,
• gsinfully,
• gainfilly,
• gaifully,
• gainfuly,
• gainfulyl,
• gainfullly,
• gainfullyy,
• geinfully,
• gallflly

• painfully,
• Gainful.

The adjective form of "gainfully" is "gainful".

The plural form of the word "gainfully" remains the same. It is an adverb and does not change in the plural form.

The singular form of the word "gainfully" is "gainful"