Wir schreiben einander, falls sich der Treffpunkt ändert.

We write to each other if the meeting point changes.

Breakdown of Wir schreiben einander, falls sich der Treffpunkt ändert.

• wir: we
• sich: itself
• schreiben: to write
• falls: if
• ändern: to change
• der Treffpunkt: the meeting point
• einander: each other

Questions & Answers about Wir schreiben einander, falls sich der Treffpunkt ändert.

Why is "einander" used here? Can I also say "uns"?

Both are correct. einander means “each other” (reciprocal pronoun). With schreiben the recipient is in the dative, so Wir schreiben einander = “We write to each other.”
In everyday speech Germans more often say Wir schreiben uns (… ), where uns is the dative pronoun and reciprocity is understood from context.

• Neutral/common: Wir schreiben uns, …
• Also fine (a bit bookish/formal): Wir schreiben einander, …
• You don’t combine them: not “Wir schreiben uns einander.”

Does "schreiben" need a preposition to mean “write to (someone)”?

No preposition is needed. The normal pattern is jemandem schreiben (dative): Ich schreibe dir.
Alternatives you’ll see:

• an + Akkusativ: Ich schreibe an meine Chefin. (acceptable, a bit more like “I’m writing to …” in the sense of addressing a message)
• The verb (jdn.) anschreiben: Ich schreibe dich an. (“I’ll message you / ping you”).
  But plain Ich schreibe dich (without an) is wrong.

Do I need to add “eine Nachricht” to make it clear we mean texting/messaging?

Not necessary. Modern schreiben commonly covers texting/messaging: Wir schreiben uns naturally means “We’ll text each other.” If you want to be explicit: Wir schreiben uns eine Nachricht / auf WhatsApp, etc.

Why is there a comma before “falls”?

Because falls introduces a subordinate clause, and German always uses a comma to separate subordinate clauses from the main clause.

Why is the verb at the end in the “falls” clause?

In subordinate clauses in German, the conjugated verb goes to the end: …, falls … ändert. In the main clause, the finite verb is in the second position: Wir schreiben …

Where does “sich” go: “falls sich der Treffpunkt ändert” or “falls der Treffpunkt sich ändert”?

Both are grammatical. The more typical order puts the short pronoun before the noun phrase: …, falls sich der Treffpunkt ändert. You can also say …, falls der Treffpunkt sich ändert, but the first version is stylistically preferred.

Why “sich ändern” and not just “ändern”?

ändern is usually transitive (“to change something”): Wir ändern den Treffpunkt.
To say that something changes by itself, use the reflexive: Der Treffpunkt ändert sich.
Related verbs:

• (sich) verändern: often “to (undergo) change” (can sound more gradual or substantial).
• wechseln: “to switch/replace” (e.g., den Treffpunkt wechseln).

How is “falls” different from “wenn,” “sofern,” and “ob”?

• falls ≈ “in case/if,” suggests a possible condition.
• wenn = “if/when,” broader; can mean either conditional “if” or temporal “whenever/when” depending on context.
• sofern ≈ “provided that,” a bit more formal/restrictive.
• ob = “whether,” used for indirect yes/no questions, not for conditions.
  Example: Ob sich der Treffpunkt ändert, wissen wir nicht. (We don’t know whether…)

Do I need “werden” to talk about the future?

No. German often uses the present for near-future plans and conditions: Wir schreiben …, falls … ändert.
Using werden is possible but not needed: Wir werden einander schreiben, falls … sounds heavier and is less common here.

Can I start the sentence with the “falls” clause?

Yes: Falls sich der Treffpunkt ändert, schreiben wir einander.
Note the inversion in the main clause after the comma (schreiben wir). You can optionally add dann: …, dann schreiben wir einander.

What case is “einander” here? Does it change form?

Here it’s the indirect object in the dative (recipient of schreiben). einander itself is invariable (no separate case forms). With prepositions you’ll see compounds like voneinander (from each other), füreinander (for each other), miteinander (with each other).

What is “Treffpunkt” exactly (gender, plural, register)?

der Treffpunkt (masculine), plural die Treffpunkte, meaning “meeting point/meeting place.” It’s neutral, standard vocabulary.

Is “Wir schreiben dich” correct?

Not with plain schreiben. You need the dative: Wir schreiben dir.
If you use the separable verb anschreiben, then the direct object is fine: Wir schreiben dich an.

Could I say “Falls der Treffpunkt geändert wird” instead?

Yes, that’s a passive variant: …, falls der Treffpunkt geändert wird (“if the meeting point is changed [by someone]”). Your original …, falls sich der Treffpunkt ändert is active/intransitive (“if the meeting point changes”), which is a bit more neutral and common in this context.