Learn Turkish: Bu yükseliş, asıl sorun olan düşüşü gizliyordu. - This rise was hiding the decline, which is the real problem.

Olan is the present participle of olmak (to be). It translates literally to 'being' or 'which is'. In Turkish, to use a noun phrase like asıl sorun (the real problem) to describe another noun like düşüş (decline), you connect them with olan. This forms the relative clause 'the decline which is the real problem'.

Why does düşüş take the accusative suffix to become düşüşü?

It is the direct object of the verb gizliyordu (was hiding). Because it is a specific, defined object—pointed out by the descriptive clause asıl sorun olan—it requires the definite accusative suffix -ü.

What role does the -iş or -üş suffix play in words like yükseliş and düşüş?

This suffix attaches to verb roots to create a verbal noun, indicating the act or manner of doing that verb. By adding it to yüksel- (to rise) and düş- (to fall), it creates the nouns for 'rise' and 'decline'.

Why does the verb gizliyordu use the past continuous tense instead of the simple past?

The past continuous suffix -iyordu is used because the hiding was an ongoing state or background action at that time in the past, rather than a single completed event. It translates directly to 'was hiding'.