Obtained from: website

“Most commonly known as MahJong, many variations are also known as MahJongg, Mah-Jongg, Mah-jong, Ma Jong, computerized MahJong, MahJong solitaire, solitaire MahJong, and Shanghai Mahjong.”

There is no difference in game play in relation to these various spellings.

However that site goes into the differences between traditional mahjong(g) and slot online solitaire mahjong(g).