In many contexts, the meanings are pretty much the same, but you might hear finished more often than completed in casual conversation. For example:
I've finished my shopping.
She finished the song.
He finished the race.
I could use completed in those sentences – the meaning wouldn't change, but the register might sound off.
The word completed can convey some sense of accomplishment. In the context of a race, it might work when the race is a major achievement:
He completed his first marathon last year.
Homework, though, is not really a major achievement, so I think you'd hear finished more often in casual conversation:
“Joey, where are you going? Did you finish your homework?”
That said, you might see completed in more formal contexts, such as a paper on education, or a course syllabus:
Students must complete six homework assignments during the semester.
The definite article conveys the sense of referring to a particular set or group.
King of kings
Means the king of all kings
King of the kings
Means king of that group of kings.
Best Answer
The two sentences will be understood to have the same meaning, however, the first one is the correct form.
When we want to talk about the property that is being compared between two things we use the preposition 'in'.
When we want to know what the quantity of the difference is, we use the preposition 'of'.
There is no quantity in the difference between words, so the preposition 'of' is not appropriate.