Mater filiae monstrat quomodo stamen rectum teneat, ne subtemen implicetur.

Here filiae is dative singular: to the daughter.

The verb monstrat can take:

• the person shown something in the dative
• and the thing shown as a direct object, or as a clause

So Mater filiae monstrat ... means The mother shows the daughter ... in the sense shows to the daughter.

A learner may expect filiam, but that would make daughter the direct object. In this sentence, the daughter is the recipient of the showing, not the thing being shown.

Also, filiae is one of those forms that can be ambiguous in isolation:

• dative singular
• genitive singular
• nominative plural

Here the syntax makes dative singular the right choice.

Latin often leaves possessive ideas unstated when they are obvious from context.

So Mater filiae can naturally mean a mother shows her daughter or the mother shows the daughter, depending on context.

If Latin wanted to emphasize her own daughter, it could say filiae suae. But very often suae is unnecessary, because the relationship is already clear.

Because quomodo introduces an indirect question: how.

So Latin says, literally, something like:

The mother shows the daughter how she should keep the warp straight

In Latin, indirect questions normally use the subjunctive, which is why the verb is teneat rather than an infinitive.

English often prefers how to ..., but Latin commonly uses:

• an interrogative word such as quomodo, quid, cur, ubi
• plus a finite verb in the subjunctive

The subject is understood, not expressed.

From the context, the most natural subject is the daughter: the mother shows the daughter how she should hold or keep the thread straight.

Latin very often omits subject pronouns when they can be understood from the context. So the clause means:

how she may/should keep the warp straight

with she left unstated.

Because rectum describes stamen, not the action of holding.

• rectum = straight, an adjective
• recte = straight/rightly, an adverb

Here Latin means keep the warp/thread straight, where straight is telling you the condition of stamen.

So rectum agrees with stamen:

• both are neuter singular
• and here rectum functions as an object complement or predicate adjective with the object

In other words:

• stamen rectum teneat = keep the warp straight
• not hold in a straight manner

Stamen is accusative singular, the direct object of teneat.

So:

• teneat = may/should hold/keep
• stamen = the thing being held/kept

A useful thing to notice is that stamen is a neuter third-declension noun, so its nominative and accusative singular look the same. That is why you have to determine its case from its role in the sentence, not from the ending alone.

It is a negative purpose clause.

• ne
  • subjunctive = so that ... not, lest
• implicetur is subjunctive because it is inside that purpose clause

So the sense is:

so that the weft may not get tangled or lest the weft become tangled

This is a very common Latin pattern:

• ut
  • subjunctive = positive purpose
• ne
  • subjunctive = negative purpose

Implicetur is present passive subjunctive from implicare.

Latin uses the passive here because the weft is the thing that might become entangled or get tangled.

So:

• subtemen is the subject
• implicetur means may be/get entangled

That makes subtemen nominative singular.

Just like stamen, subtemen is a neuter third-declension noun, so its nominative and accusative singular have the same form. The verb tells you it is the subject here.

They are subjunctive for different immediate reasons:

• teneat is subjunctive because it is in an indirect question after quomodo
• implicetur is subjunctive because it is in a purpose clause after ne

They are present subjunctive because the main verb monstrat is present, so the sentence follows primary sequence.

Very roughly:

• present main verb → present/perfect subjunctive in dependent clauses
• past main verb → often imperfect/pluperfect subjunctive

So if the main verb were past, you might expect forms like teneret and implicaretur instead.

It is natural Latin word order, but Latin is much freer than English.

The sentence begins with the main frame:

Mater filiae monstrat
The mother shows the daughter

Then it gives:

• how this is done: quomodo stamen rectum teneat
• for what purpose: ne subtemen implicetur

Latin often places important words where they are most effective for emphasis, not where English would normally put them. So the order is not random, but it is also not rigidly fixed the way English word order often is.

Yes. Both are good ways to understand it.

Quomodo literally has the sense of how, in what way, by what method. In this sentence it introduces the method the daughter is being shown:

how to keep the warp straight

So if you read it very literally, the clause is asking in what way she should keep the warp straight.