Incorrect spelling

single-handily

Incorrect spelling, explanation: a common mistake made by English users is to spell the adverb single-handedly as single-handily. While the former one is correct, the latter one is wrong as handily functions as a separate word and means in a useful way while the meaning of single-handedly is different.


Correct spelling

single-handedly

Correct spelling, explanation: grammatically speaking single-handedly is an adverb, which is created by adding the -ly ending to the adjective single-handed. The word single-handedly appeared in English in the 18th century and even then it had a meaning similar to the contemporary one.

Definition of single-handedly:
1. adverb – with no help from other people,
He is very proud of the fact that he single-handedly did up the whole flat.

Single-handedly – related expressions:
Expressions similar to single-handedly include: all on your own, all by yourself, unassisted.