أوه، نسيت الموعد.

Oh, I forgot the appointment.

Breakdown of أوه، نسيت الموعد.

• ينسى: to forget
• موعد: appointment
• أوه: oh!

Questions & Answers about أوه، نسيت الموعد.

How do I pronounce أوه، نسيت الموعد?

A careful MSA-style pronunciation is:

ʔōh, nasītu al-mawʿida
or, without full case endings in normal reading:
ʔōh, nasīt al-mawʿid

A few notes:

• أوه = oh
• نسيت is pronounced roughly na-seet in pause, or na-see-tu with the full ending
• الموعد is roughly al-maw-id, but with the Arabic sound ع in the middle: al-mawʿid

The hardest part for many English speakers is ع in موعد. If you cannot produce it well yet, that is normal.

Why is نسيت translated as I forgot even though there is no separate word for I?

In Arabic, the verb itself usually shows the subject.

نسيت means I forgot because the verb form already includes first person singular.

So Arabic does not need a separate pronoun here.
If you wanted to include I for emphasis, you could say:

أنا نسيت الموعد

But in normal Arabic, that is often unnecessary.

Why do I sometimes see نسيت and sometimes نسيتُ?

Both refer to the same verb form, but the second one shows the full grammatical ending.

• نسيت = the usual everyday spelling without short vowels