Incorrect spelling, explanation: this form is mistaken: ecomony has got n and m confused. N should be first (economy), just like in the original Greek oikonomia. Therefore the only correct English spelling is economy.

Correct spelling, explanation: the form economy is correct because the word roots go back to the Greek oikonomia (household management), where there is also n and m in such order. Therefore economy is the correct form. Ecomony is wrong since this form has these letters confused.

Definition of economy:
noun, management of resources, usually in a monetary sense
These factors are the key to understanding the Polish economy.
The global economy is said to be tripled by 2050.