Seges in illo agro bona est, et tres pulli prope gallinam currunt.

Because in takes the ablative when it means in/on in the sense of location.

So:

• in agro = in the field
• agro is ablative singular of ager

Latin uses:

• in + ablative for being in a place
• in + accusative for movement into a place

So here the crop is already located in the field, not moving into it, which is why agro is ablative.

Illo is the demonstrative adjective meaning that. It modifies agro and agrees with it in case, number, and gender.

So:

• ager = field
• agro = in the field
• illo agro = in that field

Both words are:

• masculine
• singular
• ablative

Latin often includes a demonstrative like ille, illa, illud when it wants to point something out more specifically.

Because it agrees with seges, which is a feminine noun.

In Latin, adjectives must agree with the nouns they describe in:

• gender
• number
• case

Here:

• seges = nominative singular feminine
• bona = nominative singular feminine

So bona est means is good, with bona matching seges.

Seges is nominative singular because it is the subject of est.

The basic structure is:

• Seges ... bona est = The crop ... is good

Here:

• seges = subject
• bona = predicate adjective describing the subject
• est = is

So seges has to be in the nominative.

Because tres pulli is the subject of currunt.

• pulli is nominative plural of pullus
• tres means three and agrees with pulli

Since the chicks are the ones doing the running, the phrase must be nominative plural.

Also, tres is the masculine/feminine form. That fits pulli, which is masculine plural.

Because its subject, tres pulli, is plural.

Latin verbs change form to match their subject in person and number.

• currit = he/she/it runs
• currunt = they run

Since three chicks are running, Latin uses currunt.

Because prope is a preposition that takes the accusative.

So:

• gallina = hen
• gallinam = the hen, in the accusative

And:

• prope gallinam = near the hen

This is something English speakers often need to memorize: different Latin prepositions require different cases, and prope takes the accusative.

Not necessarily. Here prope means near or close to, so it usually describes location rather than motion toward.

So prope gallinam currunt means:

• they run near the hen
• or they are running around close to the hen

If Latin wanted to emphasize movement toward a place, it would often use a different construction.

Latin word order is much more flexible than English word order because Latin uses case endings to show what each word is doing.

English depends heavily on order:

• The chicks run near the hen

Latin can move words around more freely because the endings already tell you:

• pulli = subject
• gallinam = object of prope
• currunt = plural verb

So Seges in illo agro bona est, et tres pulli prope gallinam currunt is a perfectly natural Latin arrangement, even though it does not match English word-for-word.

Seges usually means a crop, a field of grain, or growing grain/corn depending on context.

So in this sentence it is not just any plant life in general. It suggests an agricultural crop, especially something like grain growing in a field.

That is why in illo agro fits it naturally: The crop in that field is good.

Sometimes yes. Latin often omits a form of to be when it is easy to understand.

So Seges in illo agro bona could, in the right context, still mean The crop in that field is good.

But including est is completely normal and often clearer for learners.

Et simply means and and joins the two clauses:

• Seges in illo agro bona est
• tres pulli prope gallinam currunt

So the sentence is just connecting two facts:

• the crop is good
• the three chicks are running near the hen

Latin also has other ways to connect ideas, but et is the most straightforward one here.