Learn Arabic (Modern Standard): يجب أن نغادر فورا.

In Arabic, يجب is an impersonal verb that literally translates to 'it is necessary'. It almost always stays in the third-person masculine singular form. The person who actually has to do the action is indicated in the second verb, which is why we use the 'we' form نغادر (we leave) after أن.

What vowel ending should نغادر take in this sentence?

It takes a fatha on the final letter, making it نغادرَ (nughadira). This is because it directly follows the particle أن (that), which forces the present tense verb into the subjunctive mood.

Could I use a verbal noun (masdar) here instead of أن نغادر?

Yes! Instead of using أن plus a conjugated verb, you can use the verbal noun. You could say يجب المغادرة (literally 'departing is necessary'). Both structures are extremely common and interchangeable in Modern Standard Arabic.

Why does فورا end with an alif and two fathas?

The two fathas (tanwin fatha) mark the accusative case. In Arabic, applying this ending to certain nouns or adjectives is the standard way to create an adverb. Here, it turns the noun فور (immediacy) into the adverb فورا (immediately).