with intention; in an intentional manner
"he used that word intentionally"
"I did this by choice"
In an intentional manner; on purpose.
"She looked at him intentionally to make sure he noticed her arrival."
In plain English: Intentionally means doing something on purpose rather than by accident.
"She intentionally hid her keys so he wouldn't find them immediately."
The word comes from combining intentional with the suffix -ly. It entered English as an adverb meaning "in a deliberate manner."