Quarta hora iam est.

Because hora is a feminine noun, and the adjective/ordinal quarta must agree with it in gender, number, and case.

• hora = feminine singular
• so quarta = feminine singular too

This is normal in Latin: adjectives match the nouns they describe.

Examples:

• primā hora = at the first hour
• sexta hora = the sixth hour

It is an ordinal numeral, which behaves like an adjective.

Latin distinguishes between:

• cardinal numbers: ūnus, duo, trēs... = one, two, three
• ordinal numbers: prīmus, secundus, tertius, quārtus... = first, second, third, fourth

So quarta hora literally means the fourth hour.

Latin has no definite article like English the.

So quarta hora can mean:

• the fourth hour
• or sometimes just fourth hour, depending on context

Latin leaves that idea to context instead of using a separate word.

Because the subject is singular: quarta hora = the fourth hour.

So Latin uses:

• est = is for singular
• sunt = are for plural

The sentence is literally structured like:

• Quarta hora = the fourth hour
• iam = already / now by this time
• est = is

So: It is already the fourth hour.

Yes. Quarta hora is in the nominative singular, and it functions as the subject.

In English, we often say it is the fourth hour, where it is a dummy subject. Latin does not need that kind of empty it here. It can simply say:

• Quarta hora est = It is the fourth hour

So the real idea being stated is the fourth hour exists / has arrived / is now.

Iam usually means already, now already, or by now.

In this sentence it adds the idea that the time has reached that point:

• Quarta hora est = It is the fourth hour.
• Quarta hora iam est = It is already the fourth hour / By now it is the fourth hour.

So iam gives a sense of progression in time.

Latin word order is more flexible than English word order. A short adverb like iam is often placed near the word or phrase it emphasizes, but there is not just one possible position.

All of these could be understandable Latin, though style and emphasis may differ:

• Quarta hora iam est
• Iam quarta hora est
• Quarta iam hora est

The given order is natural and emphasizes that the hour has already come.

Not necessarily. In Roman timekeeping, hours were traditionally counted from sunrise, and daylight was divided into twelve hours. That means the fourth hour was not always exactly our modern 10:00 a.m.; its exact length varied with the season.

So in a Roman context:

• prima hora = first hour after sunrise
• quarta hora = fourth hour after sunrise

In a simple classroom sentence, though, it is often best understood just as it is the fourth hour.

It could be. Latin allows more than one word order.

Compare:

• Quarta hora est
• Hora quarta est

Both can mean It is the fourth hour.

However, putting the adjective first, quarta hora, is very common and natural. The choice of order can slightly affect emphasis or style, but both are grammatically possible.

Yes. Latin often uses different cases with hora depending on what you want to say.

For example:

• quarta hora est = it is the fourth hour (nominative, subject)
• quartā horā = at the fourth hour (ablative of time when)

So if you are just naming what time it is, you get:

• quarta hora est

If you are saying when something happens, you often get:

• quartā horā venit = he comes at the fourth hour

That difference is very common and worth noticing.

Yes, completely.

Latin often says things more compactly than English. This sentence has everything it needs:

• quarta hora = subject
• iam = adverb
• est = verb

English often adds a dummy it:

• It is already the fourth hour

Latin simply does not need that extra word.