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.
They are both nouns and both mean a lack of discipline. However, the word undiscipline is far less common than indiscipline. The latter can be found in most dictionaries, while most dictionaries will not contain undiscipline.
Far more common is the use of undisciplined as an adjective. Though even in this context it would probably be more idiomatic to use a negation of the word disciplined instead, compare:
- He is rather undisciplined.
- He is not very disciplined.
Best Answer
This sentence uses the indefinite article before the "majority of the students". This has the effect of introducing this group of students to the reader or the listener.
It may give a hint that the exact number of the students that will vote is uncertain: it could be 51%, but then it could be 88%.
I would also half-expect the following sentences to contain further information on this particular group of students, like this:
Now, to the second sentence.
This sentence seemed not very natural to me, but it is probably okay. It uses the definite article before "majority of the students", as if referring to a known group. But in reality it likely refers to the concept of majority (superiority in numbers).
I've tried to look for similar structures on the web, say "The majority of the citizens", "The majority of the voters", and the results are scarce (about 400 google-hits each). But so are the results for the same phrases with a, so I'm unsure.
Here's one quote apparently coined by a native English speaker:
Here, the majority is contrasted with the minority, and this probably makes the nouns "definite": we are all accustomed to groups of people being divided into a majority and a minority on numerous matters. This use of the probably stresses that the author talks about definite concepts, not about particular groups of people.
1. The grammar: "partitive structures"
As I understand it, constructions of the type
(A/The) Z of Xhave a partitive effect: we tend to assume that Z is part of X. Hence, the use of the is justified only when the reader is familiar with this particular group Z that is part of X.The writer can oftener safely presume that all his readers are familiar with abstract concepts than with some particular groups of people or items. Hence, this partitive use of the seems to prevail in phrases speaking about well-known abstract topics:
The word majority is a collective noun and could be treated either as a plural noun or as a singular noun. But following a it is usually plural, especially in of-partitive structures:
Here's one explanation I've found on the web (Grammar Logs, 2000):
Here's the Google Ngram comparison for "majority of __ is" vs. "majority of __ are" (kudos to Damkerng T.)
(Bear with me, I'm not a native English speaker and might be mistaken in my apprehension of articles.)