Die Leihfrist endet heute.

Because Leihfrist is a feminine noun in German, so its nominative singular article is die.

In this sentence, die Leihfrist is the subject, so German uses the nominative case:

• die Leihfrist = the loan period / borrowing period

A learner has to memorize the gender along with the noun:

• die Leihfrist
• not der Leihfrist
• not das Leihfrist

Leihfrist is a compound noun meaning the period of time something may be borrowed.

It is made up of:

• Leih- from leihen = to lend / borrow (depending on context)
• Frist = deadline, allotted period, time limit

So die Leihfrist is something like:

• loan period
• borrowing period
• checkout period in a library context

In everyday use, you will often see it in libraries.

Because all German nouns are capitalized.

So in this sentence:

• Die = article
• Leihfrist = noun, therefore capitalized
• endet = verb, not capitalized
• heute = adverb, not capitalized

This is a basic rule of German spelling:

• das Buch
• die Frist
• der Tag

All those nouns begin with a capital letter.

Because the subject is die Leihfrist, which is third person singular: it ends.

The infinitive is:

• enden = to end

The present-tense conjugation is:

• ich ende
• du endest
• er/sie/es endet
• wir enden
• ihr endet
• sie/Sie enden

Since die Leihfrist is singular, German uses:

• Die Leihfrist endet heute.

Because in a normal German main clause, the finite verb usually goes in position 2.

Here the sentence structure is:

1. Die Leihfrist
2. endet
3. heute

This is the standard verb-second pattern.

You could also move another element to the front, but the verb still stays second:

• Heute endet die Leihfrist.

That is also correct. German cares strongly about the verb being in second position in main clauses.

Heute is an adverb meaning today. In German, adverbs of time are often placed after the verb or later in the sentence.

So:

• Die Leihfrist endet heute. = natural
• Heute endet die Leihfrist. = also natural, with more emphasis on today

Both are correct. The difference is mostly about focus:

• Die Leihfrist endet heute. → neutral statement
• Heute endet die Leihfrist. → emphasizes today

Yes. Endet is in the simple present tense.

German uses the present tense very often for:

• general facts
• current situations
• scheduled or near-future events

So Die Leihfrist endet heute literally uses the present tense, but in English it may be translated as:

• The loan period ends today
• The due date is today
• The borrowing period expires today

German does not need a separate future form here.

Yes, that is possible, but it is a slightly different structure.

Compare:

• Die Leihfrist endet heute. = The loan period ends today.
• Die Leihfrist ist heute zu Ende. = The loan period is over today / comes to an end today.

The version with endet is very direct and common.
The version with zu Ende sein is also correct, but feels a bit more like describing a state or completion.

They are related, but not always exactly the same.

• Leihfrist = the period during which you may keep a borrowed item
• Rückgabefrist = the deadline by which you must return it

In many library contexts, they may refer to almost the same practical date. But the emphasis is different:

• Leihfrist focuses on the borrowing period
• Rückgabefrist focuses on the return deadline

In a library, Die Leihfrist endet heute usually means something like:

• Your borrowing period ends today
• This item is due today
• The loan expires today

So even if the literal meaning is The borrowing period ends today, the natural English meaning in context is often simply:

• It’s due today.

A helpful approximation is:

• Leih sounds roughly like English lie
• Frist rhymes closely with English frist in frist-like pronunciation, with a short i as in sit

So approximately:

• LIE-frist

Also note:

• ei in German is usually pronounced like English eye
• st at the end is usually pronounced as st

Normally, no. In a full standard sentence, you would usually keep the article:

• Die Leihfrist endet heute.

German often needs an article with singular countable nouns, just like English often needs the or a.

You might see article-less wording in:

• headings
• forms
• labels
• short notices

For example, a website or app might display:

• Leihfrist endet heute

But in normal sentence grammar, die is the standard form.