هو يغير الموعد.

With full vowels, it is:

هُوَ يُغَيِّرُ الْمَوْعِدَ

A careful reading is:

huwa yughayyiru al-mawʿida

If you stop at the end of the sentence, the final short vowel is usually not pronounced, so you will often hear:

huwa yughayyiru al-mawʿid

A few pronunciation notes:

• هُوَ = huwa
• يُغَيِّرُ has a doubled y sound because of the shadda
• الْمَوْعِدَ contains the consonant ع, which does not exist in English

Yes, يُغَيِّرُ already tells you the subject is he.

So Arabic can say simply:

يُغَيِّرُ الْمَوْعِدَ

and that already means he changes / is changing the appointment.

Adding هو can:

• make the subject clearer
• add emphasis
• create contrast, as in he changes it, not someone else

So هو is not always necessary, but it is perfectly natural.

It is the imperfect verb form in Arabic, which often corresponds to the English present.

Depending on context, it can mean:

• he changes
• he is changing
• he changes regularly
• sometimes even he will change

Arabic does not divide these meanings in exactly the same way English does. Context tells you which meaning is intended.

Most normal Arabic writing leaves out short vowels and other pronunciation marks.

So يغير is normally written without showing that it is actually:

يُغَيِّرُ

That means learners have to rely on:

• vocabulary knowledge
• grammar
• context

In this sentence, the correct reading is yughayyiru, not some other possibility, because it is the common present form of the verb غيّر.

The base verb is:

غَيَّرَ = to change / to alter

The form in the sentence, يُغَيِّرُ, is the he form in the imperfect:

• غَيَّرَ = he changed
• يُغَيِّرُ = he changes / is changing

This verb comes from the root:

غ ي ر

which is associated with change or difference.

Because the verb is really:

يُغَيِّرُ

The mark called shadda on ي means that consonant is doubled.

So it is not a simple yu-gha-yi-ru. It is more like:

yu-ghay-yi-ru

This doubling is an important part of the verb pattern. It helps show that the verb is from Form II:

• past: غَيَّرَ
• present: يُغَيِّرُ

الـ is the definite article, like the in English.

So:

• الموعد = the appointment / the scheduled time
• موعد = an appointment / a scheduled time

In this sentence, الموعد refers to a specific appointment or scheduled time, not just any one.

It is the direct object of the verb.

The verb يُغَيِّرُ is doing something to الموعد. In other words, the appointment is the thing being changed.

In fully vowelled Arabic, the direct object here is accusative:

الْمَوْعِدَ

The final -a shows the accusative case. In ordinary writing, that ending is usually not written.

الموعد usually means:

• appointment
• scheduled time
• meeting time
• sometimes date in the sense of a planned time

It usually does not mean a romantic date unless the context clearly points that way.

So in many everyday contexts, الموعد is best understood as a scheduled appointment or time.

Yes. This sentence uses a subject + verb + object order:

هو + يغير + الموعد

Arabic also often uses verb + subject + object, especially in more formal styles. Since the subject here is just the pronoun هو, Arabic would very often simply say:

يغير الموعد

So this version with هو is natural, but it is slightly more explicit or emphatic than the shorter version.

These are two sounds English speakers often find difficult.

• غ in يُغَيِّرُ is a voiced throaty sound, somewhat similar to the French or Parisian r, but not exactly the same.
• ع in الموعد is a deep throat sound with no true English equivalent.

A useful strategy is:

• listen to native recordings
• imitate slowly
• avoid replacing ع completely with nothing, if possible

Even if your pronunciation is not perfect at first, learners are usually understood from context.