Learn Hardcore Portuguese (Portugal): Se a consulta atrasar, vou remarcar para a tarde. - If the appointment is delayed, I will reschedule for the afternoon.

It’s the future subjunctive. Portuguese uses the future subjunctive after se to talk about a possible future event. For regular -ar verbs like atrasar, the 1st and 3rd person forms look the same as the infinitive.

Future subjunctive of atrasar: eu/ele atrasar, tu atrasares, nós atrasarmos, vós atrasardes, eles atrasarem.
Compare: English uses present (“if the appointment is late”), but Portuguese uses future subjunctive (“Se a consulta atrasar…”).

Why can’t I say Se a consulta vai atrasar?

In standard usage, Portuguese avoids future or periphrastic future in the se-clause for open possibilities. You typically use the future subjunctive: Se a consulta atrasar, ….

You might hear Se vai atrasar, … only when the speaker already treats the delay as practically certain (e.g., you can already see it happening), but the default neutral, grammatical choice is future subjunctive.

Do I need the reflexive form (atrasar-se) here? Is Se a consulta se atrasar okay?

Both are acceptable:

Se a consulta atrasar, … (non‑reflexive) — very common for events being delayed.
Se a consulta se atrasar, … (reflexive) — also used, a bit more personal/colloquial in tone. If you use the reflexive, keep the clitic before the verb in this clause: Se a consulta se atrasar (not ✗ atrasar-se here, because se-clauses trigger proclisis).

What’s the difference between atrasar and demorar?

atrasar = to be late/delayed relative to a schedule. Focus: lateness vs. the planned time. Ex.: A consulta atrasou (the appointment ran late).
demorar = to take time/last. Focus: duration. Ex.: A consulta demorou 40 minutos (it took 40 minutes).
If you mean “run late,” prefer atrasar.

Why vou remarcar instead of irei remarcar or remarco?

vou remarcar (ir + infinitive) = very common, natural spoken future; a plan or intention.
irei remarcar (simple future) = more formal/written or slightly more distant/pondered.
remarco (present) = can also express near future in Portuguese when it’s scheduled/decided, but here vou remarcar sounds the most neutral and conversational.

Is remarcar the right verb? How about adiar or reagendar?

remarcar = to reschedule (set a new time). Ex.: remarcar para as 16h.
adiar = to postpone (may or may not specify a new time). Ex.: adiar a consulta.
reagendar = exists and is understood; more bureaucratic/corporate tone. In everyday EP, remarcar is the go‑to.

Why para a tarde and not à tarde?

para a tarde = “to the afternoon” (movement/rescheduling to that slot).
à tarde = “in the afternoon” (general time of day).
With rescheduling, you normally use para: remarcar para a tarde.
Note: à has a grave accent in à tarde (contraction of a + a), but here we need para a (no contraction in writing).

Is the article needed in para a tarde? Could I say para tarde?

Use the article with time-of-day nouns: para a tarde is the normal phrasing.
You drop the article if you use an adverb like mais: para mais tarde (“for later”).

Can I say de tarde or na tarde?

de tarde (“in the afternoon”) is much more typical in Brazilian Portuguese; in European Portuguese, prefer à tarde.
na tarde is only used when specifying a particular day/period: na tarde de terça-feira (“on Tuesday afternoon”). Not with generic rescheduling.

If I want to say “reschedule it,” where does the pronoun go?

For consulta (feminine), use a:

Neutral: Se a consulta atrasar, vou remarcá-la para a tarde.
With a trigger like não, use proclisis: Se a consulta não atrasar, não a vou remarcar.
In formal writing, attaching the clitic to the infinitive (remarcá-la) is safest. Colloquial EP also allows placing it after vou: vou-lhe ligar, but for direct objects, the infinitive attachment is a clear choice.

What exactly does consulta mean here?

In Portugal, consulta typically refers to a medical/dental consultation (the appointment itself).
For non-medical contexts:

reunião = meeting
compromisso = appointment/engagement (general)
marcação = a booking (the act/slot), not the meeting itself

How do I say “If I’m late for the appointment, …” instead?

Use the reflexive with the subject “I”:

Se eu me atrasar para a consulta, vou ligar para a clínica.
Here again, se
- future subjunctive (me atrasar). You can also say Se eu chegar atrasado/atrasada à consulta, … (arrive late).