Formica parvam glandem per truncum iacentem trahere conatur.

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

• formica = nominative singular, ant
• conatur = tries

So formica conatur means the ant tries.

Because glandem is the accusative singular, which is the form used for the direct object.

The dictionary form is:

• glans, glandis = acorn

In this sentence, the acorn is what the ant is trying to drag, so Latin uses the object form:

• nominative: glans
• accusative: glandem

This is a normal third-declension pattern.

Because parvam describes glandem, and Latin adjectives must agree with the nouns they describe in:

• gender
• number
• case

So:

• glandem = feminine, singular, accusative
• parvam = feminine, singular, accusative

That is why you get parvam glandem = a small acorn.

In Latin, adjective position is much more flexible than in English. Both of these are possible in many contexts:

• parvam glandem
• glandem parvam

Here parvam glandem is perfectly normal. Because the endings already show the relationship, Latin does not depend as heavily on word order as English does.

Because it comes after per, and per takes the accusative case.

So:

• per truncum = through/across/along the trunk

Whenever you see per, you should usually expect the next noun to be accusative.

iacentem is a present participle from iaceo, meaning lying or lying on the ground.

So truncum iacentem means something like:

• a lying trunk
• more natural English: a fallen trunk / a trunk lying on the ground

A participle is verbal in meaning but adjectival in form, so here it describes truncum.

It is most naturally read with truncum because it stands right next to it inside the phrase:

• per truncum iacentem

So the phrase works as a unit: through/across the fallen trunk.

Also, iacentem agrees with truncum in number and case. In form, iacentem could also look feminine accusative singular, so an English speaker might wonder if it could describe glandem. In practice, its position strongly connects it to truncum, and the meaning fallen trunk is the natural one here.

Because it depends on conatur.

• conatur = tries
• trahere = to drag

Latin often uses an infinitive after verbs like conor to show the action being attempted. So:

• trahere conatur = tries to drag

English also uses an infinitive here, so this part matches English fairly well.

Because conor, conari is a deponent verb.

A deponent verb:

• has passive-looking forms
• but an active meaning

So even though conatur looks passive at first glance, it means:

• he/she/it tries

not is tried.

This is a very common thing for Latin learners to notice and ask about.

Not especially for Latin. Latin word order is relatively flexible because the endings show each word’s role.

This sentence puts the main ideas in a natural Latin order:

• Formica = subject first
• parvam glandem = object early
• per truncum iacentem = prepositional phrase
• trahere conatur = infinitive + main verb at the end

A more English-like order would be possible, but Latin often prefers to place the main finite verb near the end.

Because Classical Latin has no articles.

So formica can mean:

• an ant
• the ant

and glandem can mean:

• an acorn
• the acorn

You figure out which is meant from the context. This is very normal in Latin and is one of the first things English speakers have to get used to.