Ни один студент не опоздал на семинар.

Ни один means not a single or no ... at all. It is stronger and more emphatic than a simple no.

So:

• Ни один студент не опоздал = Not a single student was late
• It highlights that the number of late students was exactly zero

Yes, it is a double negative by English standards, but this is completely normal in Russian.

With negative pronouns and expressions such as никто, ничто, никогда, ни один, Russian normally also uses не with the verb:

• Ни один студент не опоздал
• Никто не пришёл
• Ничего не случилось

So in Russian, this structure is correct and expected. You should not try to avoid the second negative the way you would in standard English.

Because ни один literally means not one. Grammatically, the phrase is singular, so the noun after it is also singular:

• ни один студент
• ни одна студентка
• ни одно письмо

Even though the meaning refers to a whole group, Russian treats it grammatically as one student = singular.

In the past tense, Russian verbs agree with the subject in gender and number.

Here the subject is ни один студент, which is:

• singular
• masculine

So the verb is опоздал.

Compare:

• Ни один студент не опоздал = not a single male student / no male student was late
• Ни одна студентка не опоздала = not a single female student was late
• Ни одно письмо не пришло = not a single letter arrived

Опоздал is the past tense of опоздать, which means to be late, to arrive late, or to come too late.

So не опоздал means:

• was not late
• did not arrive late

In this sentence, natural English translations include:

• No student was late for the seminar
• Not a single student arrived late to the seminar

Because Russian does not need a separate auxiliary verb like English was here.

English says:

• was late

Russian uses one verb:

• опоздал

So не опоздал already contains the whole idea of was not late / did not arrive late.

Студент is in the nominative singular because it is the subject of the sentence.

The basic subject form is used here:

• студент = nominative singular

Even though the sentence is negative, the subject still remains nominative.

Семинар is in the accusative singular after the preposition на.

Here на семинар means to the seminar or for the seminar, in the sense of going/coming and being late for an event.

With events and scheduled activities, Russian often uses:

• на лекцию = to the lecture
• на урок = to class
• на семинар = to the seminar

Since семинар is masculine and inanimate, its accusative singular looks the same as the nominative:

• nominative: семинар
• accusative: семинар

Because with many events, classes, and organized activities, Russian uses на rather than в.

So you say:

• на лекцию
• на концерт
• на урок
• на семинар

This is about attending an event, not physically being inside something.

Using в would usually suggest being inside a place or space, and в семинар is not how Russian expresses this idea.

Yes. That is also correct, but the nuance is a little different.

• Ни один студент не опоздал на семинар = Not a single student was late
  This is more emphatic.
• Никто из студентов не опоздал на семинар = None of the students were late
  This often sounds a bit more neutral and refers clearly to a known group of students.

Both are natural. The version with ни один puts stronger focus on the idea of not even one.

Yes. Russian word order is flexible, and changing it changes emphasis more than basic meaning.

The given sentence is a neutral, natural order:

• Ни один студент не опоздал на семинар

You could also say:

• На семинар ни один студент не опоздал
  This emphasizes the seminar
• Не опоздал на семинар ни один студент
  This sounds more literary or emphatic

So the original version is a very good default form for learners.

The stresses are:

Ни оди́н студе́нт не опозда́л на семина́р.

Approximate pronunciation:

• ni a-DEEN stoo-DYENT ne a-pa-zDAL na si-mi-NAR

The most important stresses to remember are:

• оди́н
• студе́нт
• опозда́л
• семина́р

No. That would change the meaning and sound wrong in this context.

This is a very important trap:

• ни один студент = not a single student
• не один студент = more than one student / not just one student

So:

• Ни один студент не опоздал = No student was late
• Не один студент опоздал = More than one student was late

That one extra letter completely changes the meaning.

Опоздал is from the perfective verb опоздать, and here it works well because it refers to the completed result: whether someone ended up arriving late or not.

• не опоздал = did not arrive late / was not late

The imperfective опаздывать usually suggests repeated, habitual, or ongoing lateness:

• Студент часто опаздывал = The student was often late
• Он опаздывал на семинары весь семестр = He kept being late to seminars all semester

So in this sentence, опоздал is the natural choice.