L'altezza minima è sul cartello.

Because altezza is a feminine singular noun, so its basic article is la. But before a vowel, la usually drops the final a and becomes l':

• la casa
• l'altezza

This is called elision. It makes the phrase easier to pronounce.

In Italian, every noun has a grammatical gender, and altezza happens to be feminine. That is why it takes feminine forms:

• l'altezza
• minima

This gender is grammatical, not necessarily logical. A learner usually just has to memorize the noun together with its gender.

Because adjectives in Italian usually agree with the noun they describe in gender and number.

Here, altezza is:

• feminine
• singular

So the adjective must also be feminine singular:

• altezza minima

Compare:

• il valore minimo = masculine singular
• l'altezza minima = feminine singular
• le altezze minime = feminine plural

It is a noun phrase made of:

• altezza = noun
• minima = adjective

The adjective comes after the noun, which is very common in Italian. So Italian often says:

• altezza minima

where English might say minimum height.

This is a very common difference between the two languages.

The accent matters because è and e are different words:

• è = is
• e = and

So in this sentence, è is the 3rd person singular of essere:

• L'altezza minima è sul cartello.
• The minimum height is on the sign.

Without the accent, it would be the wrong word.

Sul is the contraction of:

• su = on, on top of
• il = the

So:

• su + il = sul

Because cartello is a masculine singular noun, il is the article it uses, and after su they combine into sul.

Other similar combinations are:

• su + lo = sullo
• su + la = sulla
• su + i = sui
• su + gli = sugli
• su + le = sulle

Because cartello is masculine singular, so it uses il, not la.

That means:

• il cartello
• su il cartello → sul cartello

You would use sulla only with a feminine singular noun, for example:

• la porta
• sulla porta

Italian uses su when something is physically on a surface, including writing or information appearing on a sign, label, page, or poster.

So sul cartello means the information is on the sign.

Examples:

• È scritto sul muro. = It is written on the wall.
• Lo trovi sul foglio. = You find it on the sheet of paper.
• Il prezzo è sul cartello. = The price is on the sign.

Using in would suggest inside something, which is not the idea here.

The subject is L'altezza minima.

The structure is:

• L'altezza minima = subject
• è = verb
• sul cartello = prepositional phrase showing location

So literally the sentence is built like:

• The minimum height
  • is
    • on the sign

The normal, neutral order is:

• L'altezza minima è sul cartello.

But Italian can sometimes change word order for emphasis. For example:

• Sul cartello c'è l'altezza minima.

That sounds a bit different in focus, more like The minimum height is on the sign with emphasis on where the information appears.

For a learner, the original order is the safest and most standard.

Yes. In real-life contexts, altezza minima can refer to the minimum allowed or required height, and depending on the situation it may relate to things like a restriction, a requirement, or a posted measurement.

For example, on road or parking signs, Italian often uses altezza to talk about height limits or clearance. The exact interpretation comes from context.

A simple pronunciation guide is:

• L'altezza ≈ lal-TET-tsa
• minima ≈ MEE-nee-ma
• è ≈ eh
• sul ≈ sool
• cartello ≈ kar-TEL-lo

A few helpful points:

• zz in altezza is pronounced like tts
• è is an open e sound
• stress falls on:
  • altezza → -tez-
  • minima → mi-
  • cartello → -tel-

In a normal full sentence, no: you would usually keep the article and say:

• L'altezza minima è sul cartello.

Italian often uses the definite article where English may or may not. Without the article, the sentence sounds unnatural in standard usage.

However, on signs, labels, or headings, you might see just:

• Altezza minima

because that is not a full sentence, just a label or notice.