Si quaestio difficilis est, discipula paulum cogitat et deinde respondet.

This is a simple, real condition.

Si means if, and both clauses use the present indicative:

• est
• cogitat
• respondet

That gives the sense of a general truth or a usual situation: if a question is difficult, the student thinks a little and then answers.

It is not a contrary-to-fact condition like if the question were difficult.

Because each one is the subject of its own clause.

• In Si quaestio difficilis est, quaestio is the subject of est.
• In discipula paulum cogitat et deinde respondet, discipula is the subject of both cogitat and respondet.

So both nouns are nominative singular, but they belong to different parts of the sentence.

Because gender and declension are not the same thing in Latin.

Quaestio is a third-declension feminine noun. Its dictionary form is quaestio, quaestionis.

A native English speaker often expects feminine nouns to look like first-declension nouns ending in -a, but Latin does not work that way. A noun can be feminine without belonging to the first declension.

So quaestio is feminine because that is its grammatical gender, not because of its nominative ending.

Because difficilis is a third-declension adjective.

Not all feminine adjectives end in -a. The adjective difficilis has:

• masculine singular nominative: difficilis
• feminine singular nominative: difficilis
• neuter singular nominative: difficile

So difficilis does agree with quaestio in gender, number, and case:

• feminine
• singular
• nominative

It just does not show that agreement with a first-declension-looking ending.

They are all present indicative active, third person singular.

• est = is
• cogitat = thinks
• respondet = answers / replies

In a sentence like this, the present tense often expresses a general or repeated action, not only something happening at this exact moment. So it works much like the English simple present in statements such as If a question is difficult, the student thinks for a moment and then answers.

Because the verb ending already tells you the person and number.

Both cogitat and respondet are third person singular, so they mean he/she/it thinks and he/she/it answers. Latin usually does not need a separate subject pronoun unless it is being emphasized.

Here, discipula already names the subject, so adding a separate she word would be unnecessary.

Here paulum means a little or for a short time, and it is being used adverbially.

So paulum cogitat means something like:

• thinks a little
• thinks for a bit
• thinks for a short time

This is a common Latin pattern: a neuter accusative form can be used almost like an adverb. You will see similar uses with words like multum and nihil in some contexts.

Deinde means then or afterwards.

It shows the sequence of actions:

1. she thinks a little
2. then she answers

So it helps organize the sentence in time. Without deinde, the basic meaning would still be understandable, but the step-by-step order would be less explicit.

No. Latin word order is fairly flexible because the endings show the grammar.

This sentence has a very natural order:

• Si quaestio difficilis est = the condition first
• discipula paulum cogitat et deinde respondet = the main action after that

But Latin could rearrange parts of it for emphasis. For example, Si difficilis quaestio est would still be understandable.

So in Latin, word order often affects emphasis and style more than the basic grammatical role.

Because respondet can mean simply she answers or she replies.

Latin does not always need to state the thing answered if it is obvious from context. Since the sentence already mentions quaestio, the reader can easily understand what she is answering.

In other contexts, Latin can add more information, for example:

• quaestioni respondet = she answers the question
• magistro respondet = she answers the teacher

But here the verb is complete enough by itself.