In hac cista satis spatii non est, itaque libros in alia cista ponimus.

Because hac is the ablative feminine singular form of hic, haec, hoc.

It has to agree with cista, which is:

• feminine
• singular
• ablative after in when in means location

So:

• nominative: haec cista = this box
• ablative: in hac cista = in this box

With the preposition in, Latin usually distinguishes:

• in + ablative = location, in / on
• in + accusative = motion into, into / onto

So in hac cista uses the ablative because it means location: the space is in this box.

Spatii is genitive singular from spatium, a neuter second-declension noun.

After words of quantity such as satis meaning enough, Latin often uses the partitive genitive. That literally means something like enough of space.

So:

• satis spatii = enough space / enough room

A learner may expect satis spatium, but that is not the normal construction here.

Because satis spatii is treated as a singular amount: enough space.

English does the same thing:

• There is enough space not
• There are enough space

Also, Latin does not need a separate dummy word like English there. It can simply say satis spatii non est.

Ponimus is:

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

It comes from ponere, meaning to put or to place.

So ponimus means we put, we are putting, or sometimes we place, depending on context.

Because libros is the direct object of ponimus.

The thing being put is the books, so Latin uses the accusative:

• nominative singular: liber
• accusative plural: libros

So libros ponimus = we put the books.

That is a very reasonable question.

The basic rule is:

• in + ablative = location
• in + accusative = motion into

So many learners would expect in aliam cistam after ponimus.

However, with verbs of placing such as ponere, Latin can sometimes use in + ablative to emphasize the resulting position rather than the motion itself. In other words, the books end up in another box.

So the sentence as given uses in alia cista, but your instinct about in aliam cistam follows the standard beginner rule and is a good one.

Alia is from alius, alia, aliud, meaning another, other, or different.

Here it agrees with cista, so it is:

• feminine
• singular
• ablative

Thus in alia cista means in another box or in a different box.

Both can sometimes be translated as another, but they are not exactly the same.

• alia usually means another / a different one
• altera often means the other one of two

So if the idea is just a different box, alia is perfectly natural. If there were exactly two boxes and you meant the second / the other of the two, altera might be more specific.

Itaque is a conjunction meaning and so, therefore, or so.

It connects the two clauses:

• there is not enough space in this box
• therefore we put the books in another box

It is a very common way to show result or consequence.

Because Latin word order is much more flexible than English word order. Latin relies heavily on case endings and verb endings, so it does not have to keep a fixed subject-verb-object pattern.

In this sentence:

• In hac cista comes first to set the scene
• non est comes at the end of the first clause, which is very natural in Latin
• libros appears before ponimus, but its accusative ending already shows that it is the object

So the order sounds Latin even though it is not the same order English would usually use.

Because Latin has no articles.

That means Latin does not have separate words for:

• the
• a / an

So cista can mean:

• a box
• the box

The context tells you which is meant. The same is true for libros: it can mean books or the books, depending on the situation.