Die Schneiderkreide markiert, wo wir abstecken.

Here Die means the, not they.

It is the feminine singular nominative article, because Kreide is a feminine noun in German, and Schneiderkreide keeps the gender of Kreide.

So:

• die Kreide = the chalk
• die Schneiderkreide = the tailor’s chalk

German capitalizes nouns, so Die at the start of the sentence is just the normal article with a capital letter because it begins the sentence.

Schneiderkreide is a compound noun, which is very common in German.

It is made from:

• Schneider = tailor
• Kreide = chalk

Together, Schneiderkreide means tailor’s chalk.

A useful rule: in German compound nouns, the last part usually determines the basic meaning and the grammatical gender. Since Kreide is feminine, Schneiderkreide is also feminine.

Because the subject is Die Schneiderkreide, which is third person singular.

The verb markieren is conjugated like this in the present tense:

• ich markiere
• du markierst
• er/sie/es markiert
• wir markieren
• ihr markiert
• sie/Sie markieren

So:

• Die Schneiderkreide markiert = The tailor’s chalk marks

Even though Schneiderkreide is a thing, German still uses the same third person singular form as with er/sie/es.

Because wo wir abstecken is a subordinate clause.

German normally uses a comma to separate a main clause from a subordinate clause:

• Die Schneiderkreide markiert, wo wir abstecken.

The first part is the main clause:

• Die Schneiderkreide markiert

The second part is the subordinate clause:

• wo wir abstecken

This comma is not optional in standard German.

Because abstecken is a separable verb, and in a subordinate clause the prefix stays attached to the verb.

In a main clause, you would usually see:

• Wir stecken ab.

Here the prefix ab- separates and goes to the end.

But in a subordinate clause, the full verb goes to the end as one unit:

• ..., wo wir abstecken.

This is a very important pattern in German:

• Main clause: Wir stehen auf.
• Subordinate clause: ..., weil wir aufstehen.

So abstecken follows the same logic.

Here wo means where.

It introduces a clause that tells you the place/location connected with the action:

• wo wir abstecken = where we mark out / pin / measure off

In sentences like this, wo often refers to an understood place, even if that place is not stated as a separate noun.

You can think of the sentence as slightly expanded:

• Die Schneiderkreide markiert die Stelle, wo wir abstecken.
• The tailor’s chalk marks the place where we ...

In natural German, that noun phrase can be left out if the meaning is clear.

Yes, many learners notice that.

German can sometimes leave the object or location more implicit than English does. Here the sentence can be understood as something like:

• Die Schneiderkreide markiert die Stelle, wo wir abstecken.

So the idea is that the chalk marks the spot / the line / the place where the next action happens.

In other words, the sentence is grammatically fine, but there is an understood location behind it.

Yes. Abstecken is built from the verb stecken plus the separable prefix ab-.

That prefix changes the meaning. In many contexts, abstecken means things like:

• to mark out
• to stake out
• to measure off
• to pin out

The exact English translation depends on the situation, but grammatically the important thing is that it is a separable verb.

That affects word order:

• Main clause: Wir stecken ab.
• Infinitive: abstecken
• Subordinate clause: ..., wo wir abstecken

Because in the subordinate clause, wir is the subject and the conjugated verb goes to the end.

German subordinate clauses usually follow this pattern:

• conjunction / relative word + subject + other elements + verb at the end

So:

• wo = introduces the clause
• wir = subject
• abstecken = verb at the end

That is why you get:

• wo wir abstecken

and not an English-like word order such as wo abstecken wir.

In German, all nouns are capitalized.

So in this sentence:

• Schneiderkreide is capitalized because it is a noun.

Words like markiert, wo, wir, and abstecken are not nouns, so they are normally lowercase.

This is one of the easiest visual clues in German for spotting nouns.

Yes, but the meaning and emphasis may change slightly.

For example, you could move the subordinate clause first:

• Wo wir abstecken, markiert die Schneiderkreide.

That is grammatically possible, but it sounds more marked and less neutral. The original version is more straightforward:

• Die Schneiderkreide markiert, wo wir abstecken.

German allows some flexibility, but the original order is the most natural if you want to present the tailor’s chalk as the topic first.