Gnomon umbram ostendit.

Because gnomon is in the nominative singular, the case normally used for the subject.

A beginner might expect a subject to end in -us or -a, but many Latin nouns do not. Gnomon is a third-declension noun, so its nominative singular happens to be gnomon.

Gnomon is a third-declension masculine noun.

A dictionary entry would normally look like this:

gnomon, gnomonis, m.

That tells you:

• gnomon = nominative singular
• gnomonis = genitive singular
• m. = masculine

The genitive form helps you see the stem: gnomon-.

Umbram is accusative singular.

It is accusative because it is the direct object of ostendit—the thing being shown.

Its base noun is umbra, a first-declension noun. The accusative singular ending of first-declension nouns is usually -am, so:

• nominative: umbra
• accusative: umbram

In this sentence, ostendit is third person singular, present active indicative of ostendere.

That means:

• third person singular = he/she/it
• present = shows
• active = the subject does the action
• indicative = a straightforward statement

So the verb ending tells you that the subject is he/she/it, and here that it refers to gnomon.

Yes. Written Latin ostendit can be either:

• present: shows
• perfect: showed / has shown

The form is the same in writing, so context tells you which meaning is intended. In a simple beginner sentence like this, it is usually understood as present unless something suggests past time.

Because Latin has no articles like English the or a/an.

So a Latin noun by itself can mean:

• a shadow
• the shadow

The context decides which English article makes the most sense.

The same is true for gnomon:

• a gnomon
• the gnomon

Not as much as in English.

Latin uses case endings to show each word’s job in the sentence, so the order can be more flexible. Here:

• gnomon = subject
• umbram = object
• ostendit = verb

Gnomon umbram ostendit is a very normal order, but Latin could rearrange the words for emphasis without changing the basic meaning.

For example, Umbram gnomon ostendit would still mean the same thing, though the emphasis might feel different.

Yes.

Because ostendit already means he/she/it shows, Latin often does not need an explicit subject pronoun or noun. So umbram ostendit could mean:

He/she/it shows the shadow.

Adding gnomon makes the subject explicit: The gnomon shows the shadow.

The ending tells you.

Umbram ends in -am, which is accusative singular for a first-declension noun.

If it were plural, you would expect umbras, the accusative plural form.

So:

• umbram = shadow / the shadow
• umbras = shadows / the shadows

Roughly like this:

GNO-mon OOM-bram os-TEN-dit

A few helpful points:

• g is always a hard g
• gn is pronounced with both sounds, not like English n alone
• u is like oo
• e in ostendit is like e in met

So gnomon is not pronounced like English NO-mon; the initial g is sounded.