Terminus et lapis terminalis fines ostendunt.

The subject is Terminus et lapis terminalis.

• Terminus = one noun in the nominative singular
• lapis terminalis = another nominative singular phrase
• et = and

So Latin is saying that Terminus and the boundary stone are the things doing the action.

Because the sentence has a compound subject: Terminus et lapis terminalis.

Even though each noun by itself is singular, two singular subjects joined by et (and) take a plural verb.

So:

• terminus ostendit = the boundary marker shows
• lapis terminalis ostendit = the boundary stone shows
• terminus et lapis terminalis ostendunt = the boundary marker and the boundary stone show

That is why the verb is ostendunt and not ostendit.

Fines is accusative plural.

It is the direct object of ostendunt, meaning it receives the action of the verb. In other words, it is what they show.

So the structure is:

• Terminus et lapis terminalis = subject
• fines = direct object
• ostendunt = verb

Yes.

The dictionary form is finis, and fines is one of its plural forms. Here it is accusative plural.

A learner should notice that finis is a third-declension noun, so its forms may not look as simple as first- or second-declension nouns.

Latin often uses the plural fines to mean boundaries, borders, or even territory.

So even if English might sometimes use a singular word like boundary, Latin very naturally uses the plural here.

Also, singular finis very often means end, while the plural fines commonly refers to limits/borders.

Lapis terminalis is a noun + adjective phrase:

• lapis = stone
• terminalis = boundary-related, marking a boundary, terminal

Together they mean boundary stone or boundary marker stone.

Grammatically:

• lapis is nominative singular masculine
• terminalis agrees with it in case, number, and gender

Because terminalis is a third-declension adjective, not a regular first/second-declension adjective.

Its nominative singular masculine/feminine form is terminalis.

Since it modifies lapis, which is masculine nominative singular, terminalis must also be masculine nominative singular. For this adjective, that form is terminalis.

So:

• not terminalus
• but terminalis

Because Latin word order is much freer than English word order.

An adjective can come before or after the noun it modifies. Here lapis terminalis is a perfectly normal order.

So:

• lapis terminalis
• and terminalis lapis

could both be understandable, though one may sound more natural depending on style and context.

The important thing is not just position, but agreement: terminalis matches lapis in case, number, and gender.

They are very close in meaning.

• terminus can mean a boundary marker, boundary point, or limit
• lapis terminalis literally means boundary stone

So they can overlap a lot. In some contexts they may be near-synonyms. In others, the writer may be mentioning two related kinds of boundary markers.

A learner should mainly see that, in this sentence, Latin treats them as two items joined by et.

Here terminus is nominative singular.

You can tell because:

• it is part of the subject
• its ending -us is a very common nominative singular ending for a second-declension masculine noun

So in this sentence terminus is the form used for the one doing the action.

Here lapis is also nominative singular.

It is another part of the subject, joined to terminus by et.

Even though lapis does not end in -us, it is still nominative singular. It belongs to the third declension, so its forms follow a different pattern from terminus.

Ostendunt is:

• present tense
• active voice
• indicative mood
• third person plural

So grammatically it means they show.

The -unt ending is the key signal here: it tells you the verb is third person plural.

Yes. Latin word order is flexible because the endings show what each word is doing.

This sentence is written in a fairly straightforward order:

• subject
• object
• verb

But Latin could rearrange the words for emphasis or style.

For example, the same basic meaning could still be expressed with different orders, because:

• Terminus is nominative
• lapis terminalis is nominative
• fines is accusative
• ostendunt is plural

So the grammar is carried mainly by the endings, not by strict position.

Because Latin does not have articles like English the and a/an.

Whether a noun should be understood as a boundary stone, the boundary stone, or simply boundary stone depends on context.

So Latin often leaves that idea unstated, and English has to supply it when translating.

Not necessarily.

Depending on context, ostendere can mean:

• show
• point out
• indicate
• make clear
• sometimes something like mark out

So in a sentence about boundaries, a translation like indicate the boundaries or mark the boundaries may feel natural in English, even though the basic verb is show.