Hirundo sub tecto volat, sed alia hirundo in ramulo prope fenestram sedet.

Because sub can take two different cases:

• ablative for location: under
• accusative for motion toward a place: to under / underneath

So in sub tecto, the swallow is already flying under the roof, not moving from somewhere else to get under it. That is why Latin uses the ablative: tecto.

A useful contrast:

• sub tecto volat = it flies under the roof
• sub tectum volat = it flies to a position under the roof

For the same basic reason. In also has a two-case pattern:

• in + ablative = in / on a place, with location
• in + accusative = into / onto a place, with motion toward

Here the second swallow is sitting in a place, not moving into it, so Latin uses in ramulo with the ablative.

In this sentence, in ramulo is best understood as on a small branch / on a twig. Latin in can cover English in, on, and sometimes at, depending on the noun and the situation.

Because prope is a preposition that simply takes the accusative.

So:

• prope fenestram = near the window

This accusative does not mean motion here. It is just the case that prope requires.

That is an important difference from prepositions like in and sub, whose case changes according to meaning.

Here alia means another or a different.

It is alia because it agrees with hirundo in:

• gender: feminine
• number: singular
• case: nominative

So:

• alia hirundo = another swallow

The dictionary form is alius, alia, aliud.

A useful nuance:

• alia hirundo = another swallow / a different swallow
• altera hirundo often means the other swallow when there are specifically two

In this sentence, alia is a very natural choice.

Hirundo is a feminine third-declension noun.

Its dictionary form is:

• hirundo, hirundinis = swallow

This can surprise English speakers because the nominative singular ends in -o, which does not look like a typical feminine ending. But in Latin, third-declension nominatives are often unpredictable, so you cannot identify the declension just from the nominative alone.

So here:

• hirundo = nominative singular, the subject
• it is feminine, which is why the adjective is alia, not alius or aliud

Classical Latin has no articles.

So a noun like hirundo can mean:

• a swallow
• the swallow

The exact meaning depends on context.

That is why:

• Hirundo sub tecto volat can be understood as A swallow is flying under the roof
• and alia hirundo as another swallow

Latin leaves that distinction to context instead of using separate article words.

Latin often repeats a noun where English would prefer a pronoun. That is especially common in simple, clear prose.

So Latin can say:

• Hirundo ... sed alia hirundo ...

where English might say:

• A swallow ... but another one ...

The repeated noun makes the contrast very clear: one swallow in one place, another swallow in another place.

A pronoun would also be possible in some contexts, but repeating the noun is perfectly natural and often clearer.

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

English depends heavily on order to show who is doing what. Latin depends much more on word endings and case forms.

So in this sentence:

• Hirundo sub tecto volat
• alia hirundo in ramulo prope fenestram sedet

the meaning is clear because:

• hirundo is nominative, so it is the subject
• tecto and ramulo are ablative after prepositions
• fenestram is accusative after prope

Latin often puts the verb later in the clause, but it does not have to. The exact order can give slight emphasis or simply reflect style.

They tell us that both verbs are:

• third person
• singular
• present tense
• active
• indicative

So:

• volat = he/she/it flies or is flying
• sedet = he/she/it sits or is sitting

They are singular because each verb has a singular subject:

• hirundo
• alia hirundo

Yes, but in English we would often translate it more naturally as is perched.

Latin sedere basically means to sit, but with birds it can describe the idea of being settled somewhere, just as English might say a bird sits on a branch or perches on a branch.

So:

• in ramulo ... sedet = is sitting / perching on a small branch

Ramulo comes from ramulus, which is a diminutive of ramus.

So:

• ramus = branch
• ramulus = little branch, small branch, twig

In the sentence, ramulo is the ablative singular after in.

So the choice of ramulus adds a small detail: the bird is not just on any branch, but on a small branch or twig.

In practice, it describes the location of the second swallow, and English will usually connect it with the branch:

• on a small branch near the window

So structurally, you can think of it as expanding the place phrase:

• in ramulo prope fenestram

But it also naturally relates to the whole action of sedet, since it tells us where the bird is sitting.

Latin often allows this kind of smooth grouping without needing extra words. The overall meaning is simply that the second swallow is sitting on a small branch that is near the window.