Si qua pars obscura est, magistra eam clare explicat.

It has two parts:

• Si qua pars obscura est = the if-clause
• magistra eam clare explicat = the main clause

So the sentence is a simple present condition:

• if some part is unclear,
• the teacher explains it clearly.

Latin often puts the if-clause first, just as English often does.

Si means if.

It introduces a condition. In this sentence, it sets up the situation under which the main action happens:

• Si ... est = If ... is
• magistra ... explicat = the teacher explains ...

Because both verbs are in the present indicative (est, explicat), this is a straightforward, real condition: if a part is unclear, the teacher explains it.

This is a very common point of confusion.

After words like si (if), nisi (unless), num, and ne, Latin often uses quis/quid or qui, qua, quod in an indefinite sense where English would often say someone, something, or any.

So:

• qua pars here means some part or any part
• not which part

In other words, qua is not interrogative here, and not relative. It is an indefinite adjective modifying pars.

So:

• si qua pars obscura est = if any part is unclear

No. Here qua does not mean which.

Even though qui, quae, quod can be a relative pronoun or interrogative adjective in other contexts, here qua is being used as an indefinite adjective because it comes after si.

So you should understand it as:

• qua pars = some part / any part

not:

• which part

Context and the presence of si tell you which meaning is intended.

Pars is:

• nominative
• singular
• feminine

Its job is to be the subject of est.

So in the clause:

• qua pars obscura est

the core is:

• pars est obscura = the part is unclear

with qua adding the sense some / any.

Because it agrees with pars.

Pars is:

• feminine
• singular
• nominative

So the adjective modifying it must also be:

• feminine
• singular
• nominative

That gives:

• pars obscura = an unclear part / a part that is unclear

This is standard Latin adjective agreement.

Obscura means dark, unclear, obscure, or hard to understand, depending on context.

In this sentence, since the topic is probably teaching or explaining, the natural meaning is:

• unclear
• difficult to understand

So pars obscura is an unclear part.

Magistra is:

• nominative
• singular
• feminine

It is the subject of explicat.

So:

• magistra explicat = the teacher explains

Because Latin marks grammatical roles with endings, magistra does not need to come first to be understood as the subject. Its ending already shows that.

Eam refers back to pars.

Since pars is feminine singular, the pronoun referring to it must also be feminine singular. So:

• pars = feminine singular
• eam = her/it in the accusative feminine singular

Here it means it:

• magistra eam explicat = the teacher explains it

So the full sense is:

• If any part is unclear, the teacher explains it clearly.

Because it is the direct object of explicat.

The verb explicat means explains, and the thing being explained is the direct object:

• magistra = subject
• explicat = verb
• eam = direct object

So Latin uses the accusative:

• eam = it

Clare is an adverb meaning clearly.

It modifies the verb explicat:

• explicat = explains
• clare explicat = explains clearly

It comes from the adjective clarus, clara, clarum (clear, bright, famous), but here it has the adverb ending -e.

Latin word order is much more flexible than English word order.

All of these would still be understandable Latin, with slightly different emphasis:

• magistra eam clare explicat
• magistra clare eam explicat
• eam magistra clare explicat

In your sentence, eam comes before clare explicat, which is a very natural arrangement. English depends heavily on word order for grammar, but Latin depends more on endings.

So the order here is normal, but not the only possible one.

Because the sentence expresses a general present situation:

• est = is
• explicat = explains

This gives the sense:

• Whenever any part is unclear, the teacher explains it clearly.

Latin often uses the present indicative for general truths, habits, or repeated actions, just as English does.

Because this is a simple, real condition, not a hypothetical or contrary-to-fact one.

The sentence is saying something factual or habitual:

• If any part is unclear, the teacher explains it clearly.

That is why Latin uses the indicative:

• est
• explicat

A learner might expect the subjunctive because some Latin conditional sentences do use it, but not all of them do. Here the indicative is exactly what you would expect for a straightforward condition.

Yes.

Pars literally means part, but in context it can refer to:

• part of a lesson
• part of a text
• part of an explanation
• part of an assignment

That is probably what is meant here. So qua pars obscura est most naturally means:

• if any part is unclear
• if some part is hard to understand

rather than a physical piece of an object.