At the beginning.
"Initially, we planned to drive to the beach, but heavy traffic forced us to take a bus instead."
In plain English: Initially means at the very beginning of something before things change later on.
"Initially, I thought the movie would be boring, but I was wrong."
Usage: Use initially to indicate that something happened at the very start of a process or situation, often implying it may change later. It correctly modifies verbs to show the timing of an action when it first occurred.
The word initially comes from combining the adjective initial with the suffix -ly to form an adverb. It entered English by attaching a common grammatical ending to the root meaning of "first."