Cum ungula equae lapidem tetigit, parvus sonus in via auditus est.

In this sentence, cum is a conjunction, not a preposition.

• As a conjunction, cum can mean when, since, or although.
• As a preposition, cum means with and is followed by the ablative.

Here, cum ungula equae lapidem tetigit is a full clause with a verb (tetigit), so cum must mean when.

Compare:

• cum amico venit = he came with a friend
• cum venit = when he came

Ungula equae means the hoof of the mare or the mare’s hoof.

Here is how it works:

• ungula = hoof
• equae = of the mare

So equae is a genitive singular form, showing possession.

A native English speaker may want to translate it naturally as:

• the mare’s hoof
• or simply the horse’s hoof, depending on context

But literally, Latin says hoof of the mare.

Because equae is in the genitive singular, not the nominative.

The subject of the first clause is ungula:

• ungula = nominative singular, so it is the thing doing the action
• equae = genitive singular, showing whose hoof it is

So the clause means:

• the mare’s hoof touched the stone

not

• the mare touched the stone

Lapidem is the direct object of tetigit.

The verb tangere means to touch, and the thing touched is put in the accusative case.

So:

• lapis = stone (dictionary form, nominative)
• lapidem = stone as direct object (accusative singular)

That is why Latin says:

• ungula ... lapidem tetigit = the hoof touched the stone

Tetigit is perfect tense, active voice, third person singular, from tangere.

It means:

• he/she/it touched
• or sometimes has touched, depending on context

Here the subject is ungula, so:

• tetigit = it touched

In a narrative sentence like this, the English translation is usually simple past:

• the hoof touched the stone

Auditus est is a perfect passive form meaning was heard.

It is made of:

• auditus = perfect passive participle of audire
• est = is, used here to form the perfect passive

So:

• sonus auditus est = a sound was heard

Latin often uses the passive when English would also use passive, especially if the hearer is unknown or unimportant. The sentence focuses on the sound itself, not on who heard it.

Because parvus sonus is the subject of the second clause.

Both words are nominative singular masculine:

• parvus = small
• sonus = sound

They agree because adjectives in Latin match the nouns they describe in:

• gender
• number
• case

Since sonus is the thing that was heard, it must be nominative:

• parvus sonus auditus est = a small sound was heard

If it were parvum sonum, that would be accusative, which would not fit here.

In via means on the road or in the road/street, and via is in the ablative because in with the ablative expresses location.

A helpful rule is:

• in + ablative = in/on somewhere
• in + accusative = into/onto somewhere

So:

• in via = on the road
• in viam = into the road

Here the sound is heard on the road, so the ablative is correct.

Latin word order is more flexible because the endings show the grammatical function of words.

English depends heavily on word order:

• the hoof touched the stone

Latin can move words around more freely because case endings tell us who is doing what:

• ungula = subject
• lapidem = object

So Cum ungula equae lapidem tetigit, parvus sonus in via auditus est is perfectly normal Latin even though it does not match English word order exactly.

The order may also help emphasis or style:

• the first clause sets the scene
• the second clause gives the result

Formally, equae could have more than one grammatical value, because first-declension endings can overlap. It can be:

• genitive singular = of the mare
• dative singular = to/for the mare
• nominative plural = mares

But in this sentence, only genitive singular makes sense:

• ungula equae = the mare’s hoof

The other possibilities do not fit the grammar or meaning well.

Because sonus is a second-declension masculine noun.

Its gender is something you simply learn with the word:

• sonus, -i, m. = sound

That is why the adjective is also masculine:

• parvus sonus

Latin adjectives must agree with the noun they modify, so parvus is masculine nominative singular to match sonus.

Yes, cum clauses can sometimes use the subjunctive, but not always.

In this sentence, tetigit is indicative, which suits a straightforward temporal meaning:

• when the mare’s hoof touched the stone

A cum clause with the subjunctive often has a more explanatory, circumstantial, or literary force, such as:

• since
• although
• when in a more descriptive background sense

So a learner should notice:

• cum + indicative often gives a simple time idea
• cum + subjunctive often adds more nuance

A useful breakdown is:

Subordinate clause

• Cum = when
• ungula = subject, hoof
• equae = genitive, of the mare
• lapidem = direct object, stone
• tetigit = verb, touched

Main clause

• parvus sonus = subject, a small sound
• in via = prepositional phrase, on the road
• auditus est = verb, was heard

So the structure is:

• When the mare’s hoof touched the stone, a small sound was heard on the road.

This kind of clause-by-clause analysis is often the easiest way to read Latin.