Learn Farsi: بر اساس مشاهده، او غایب بود. - Based on the observation, he was absent.

It perfectly follows the mo-C1-â-C2-e-C3-e pattern. The root consonants here are sh-h-d (related to witnessing or seeing). By slotting them into the pattern, we get مشاهده (mo-sh-â-h-e-d-e), meaning 'observation' or 'viewing'.

Is there a hidden ezafe between اساس and مشاهده?

Yes, the phrase is read as bar asâs-e moshâhede. The phrase بر اساس (bar asâs) is a compound preposition meaning 'based on,' and like most multi-word prepositions in Persian, it requires an ezafe to connect it to its object.

If we wanted to say 'Based on the observations' (plural), how would مشاهده change?

Because it is an Arabic verbal noun ending in the silent ـه (-e), its formal plural takes the Arabic suffix ـات (-ât). You drop the final ـه and add the suffix, resulting in مشاهدات (moshâhedât).

Is غایب (ghâyeb) also an Arabic loanword derived from a pattern?

Yes, it follows the Arabic active participle pattern C1-â-C2-e-C3 (often called the fâ'el pattern). The root consonants are gh-y-b (relating to absence or being unseen), so the pattern creates غایب, meaning 'the one who is absent' or 'absent'.