Rozměry jsou v e-mailu.

Rozměry means dimensions or measurements.

Its singular form is rozměr, which means dimension.
So:

• rozměr = dimension
• rozměry = dimensions

In this sentence, the plural is used, so it refers to more than one measurement, such as length, width, height, etc.

Because rozměry is plural.

In Czech, the verb to be changes depending on number:

• je = is for singular
• jsou = are for plural

So:

• Rozměr je v e-mailu. = The dimension is in the email.
• Rozměry jsou v e-mailu. = The dimensions are in the email.

Czech does not have articles like a, an, or the.

So Rozměry jsou v e-mailu can mean:

• The dimensions are in the email
• Dimensions are in the email

Usually the context makes it clear, and in normal English translation, the dimensions are in the email is the most natural choice.

Because the preposition v meaning in requires the locative case when it refers to location.

So e-mail changes form after v:

• basic form: e-mail
• after v: v e-mailu

This is a common Czech pattern: prepositions often require a certain case, and the noun ending changes because of that.

It is in the locative singular.

The structure is:

• v = in
• e-mailu = in the email

So v e-mailu is a prepositional phrase in the locative case.
This is one of the first case patterns learners meet in Czech, because v and na are often used with the locative when talking about location.

It is a borrowed word, based on English email.

In Czech, you may see several spellings depending on style:

• e-mail
• email

Both are commonly understood. The sentence Rozměry jsou v e-mailu is completely natural. The form v emailu is also seen in modern usage.

Yes. Czech word order is more flexible than English word order.

The neutral version is:

• Rozměry jsou v e-mailu.

But you could also say:

• V e-mailu jsou rozměry.

This might put a bit more focus on where the dimensions are. Both are grammatical. Czech often changes word order to shift emphasis, not basic meaning.

A rough pronunciation guide is:

ROZ-mnye-rih zsoh v EH-mai-loo

A few notes:

• ř in rozměry is a special Czech sound and can be hard for English speakers. If you cannot say it yet, an approximation is better than nothing.
• jsou is pronounced like zsoh or ysoh depending on the speaker, but zsoh is a useful learner approximation.
• v is often pronounced very lightly before another consonant.

Because it is a plural noun form.

The noun rozměr is masculine, and its nominative plural form is rozměry. In this sentence, rozměry is the subject, so it appears in the nominative plural.

That is why the verb is also plural:

• Rozměry = plural subject
• jsou = plural verb

Yes. Depending on context, rozměry can often be translated as:

• dimensions
• measurements
• sometimes sizes

If someone is talking about an object, package, room, or product, dimensions is usually the best translation. If the context is more general, measurements may also work.

They are very similar, but v e-mailu is more standard and clearer.

• v e-mailu = in the email
• v mailu = in the mail/email, more informal or colloquial in some contexts

For learners, v e-mailu is the safer and more standard choice.

Yes, absolutely. It is a natural, everyday sentence.

It sounds like something someone would write or say when telling another person where to find the information:

• Rozměry jsou v e-mailu.
• The dimensions are in the email.

It is short, practical, and very typical of real communication.